So I may have now reached a partial solution for this.
Those changes to the settings have dropped the general temperature of the GPU JT to about 35c. Which is about 15-20 degrees lower than it was.
Whilst playing the game as a test last night there was no Wattman crash but the JT got up to around 100c. Now I don't necessarily think that's an issue now with the GPU. I think I need to do a general temperature/fan test of the machine and case to check they're working properly.
I've one more week on online teaching.lecturing to get through and then I'll do some temperature checks in game with the case panels off etc to see if it is just an airflow issue now.
But we may have nearly cracked it now!
How to OVERCLOCK and UNDERVOLT RX 5700XT | ADRENALIN 2020 Easy Guide This video is by Ancient Gameplays. It shows you everything I explained except fan control. Apparently the 5700 XT doesn't run a "zero RPM" config but you can increase the base speed and change the curve to ramp up quicker to keep the temps down. The voltage you posted earlier is identical in the video, so your all set that way. Your power limit can go to 50, my 5600 XT only goes to 20. That extra juice is only used as needed by the GPU. 100c is actually "ok", 115c and it will throttle back. He mentions reducing GPU clock to 2000 for best performance/stability, others claim the same. The VRAM OC will work at 1800 but the lofty 1860 very well may not. For me 1800 nets 10-15 FPS, 1860 about 5 more but will "green screen".
Brand matters. If you have a THICCIII XFX card, they run 100-110c. I noticed this guys card in the video runs 63c, I think his is a Gigabyte Windforce RX 5700 XT from other videos. ASUS runs hotter, it just depends. If your fans are at like 60% or more at 50c, that's as good as it gets to hold it back from attaining that 100c. These cards heat up quick. Running with the side off is ok, but doesn't tell the true tale of airflow. General rule is intake front, side, bottom, exhaust top and rear. The idea is to get positive case pressure. So with a tissue or napkin, you can check that by seeing how good they stick to the intake vents and how well the push away from the exhaust. If it just falls off an intake area, there may be a problem. If it is only barely pushing from the exhaust area, you might want more CFM outbound. You may find with the side off the card runs hotter simply because it's lacking the positive pressure of the cool room air and relying solely on it's fans. When I take my side off while running, the fans pick up speed like covering a vacuum hose with your hand and releasing it(not as extreme).
Case matters too. I run a Fractal Design R4 S, top mounted AIO (exhaust), 2 x 140mm front intake fans at 1000 RPM (UPHERE, 49.8 CFM, 25dBA), 1 x 140mm (same brand) side intake. I use the bottom as a intake vent and rear works as an exhaust vent both no fan. Those 3 fans, combined with the AIO's 2 x 140mm PWM's, the GPUI's 2 fans, and 1 built in SB fan pull hard enough that no additional fan in needed. A napkin will stick to all intake areas and the bottom vent but the top it blow the napkin off and the rear it blows it away from the case. Noise is about 25dBA total, 30 when the card gets going but still less than a window AC. Fans blowing in all kinds of direction create a static flow of swirling air that doesn't exchange the warm air inside with cooler room air fast enough. There's a video on a case with 12 fans and a heat issue, lol. It shows what I mean about pressurizing the case but not exchanging air.
So with airflow, the general idea is to fill the case with air and exchange it with room air every 30 seconds or so. Just enough time for the air to carry some heat off the chips/radiator. Too quick and it'll heat up because the air didn't have time to soak some of the heat off the internals. If you have a sensor for internal case temp. it should read about 5-10 warmer than room temp and you're fine.
An over explanation of things you may already know. Hopefully you get something out of it all. At the end if 100c is what the card runs at and works fine, let it be.
So it looks like this might be solved now.
I've had new fans installed in my PC and they're working well. The new power settings mean that the GPU fan is working to deal with the temperature when playing Total War.
The JT is getting up to around 80 degrees ish but, as of yet, no carshes again or anything similar.
It may well be that's the temperature it runs at for that game. If the power settings are dealing with it, and my new fans are circulating the air ok, then it should all be good now.
If that changes I'll return here but for now: thanks everyone!
I follow your fix using 20.9.1 and works fine with my msi 5700 xt gaming X and z490.
I only have a question: how is the best profile for gaming (more stable): gaming, esports, standard, power saving???
I usually use esports but other fixes only recommend standard profile.
When you use the "fix" you're skipping the "profile presets" for power, etc. Use "custom" and leave everything off but perhaps "image sharpening" (I set mine to 20%) and "surface optimization" is on. The other stuff just messes things up, in my opinion. Some has no effect at all. Use FreeSync if your monitor has it. If not, use in game frame limiter settings to match your refresh rate instead of "enhanced sync". If the game doesn't have a frame limit setting, skip it and just run the game. BTW, the "fix" is for the 20.8.3 driver mainly.
Thanks @mackbolan777 for your quick response.
The Game/esports mode active the amd anti-lag option that seams interesting for gaming (but if this options cause problems, I will let it disable)
I read a post from @RPX100 who uses your “fix” with the 20.9.1 and works fine for him, but I can reinstall the 20.8.3 and check.
@iTruji I am currently on 20.11.2 and it is still working fine for me.
I am still on Standard Profile and have custom fan curve (hot spot max 85°C) and undervolted my card.
All that anti-lag, radeon chill, stuff is of no help and can incur a performance hit or undesired operation. It's simply a "click n go" solution for those who want to experiment with features with a click rather than try each thing to see if you benefit. Persoanlly and Fabio would say the same, is to just use the "custom" and leave all the stuff off completely. I personally like the image sharpening at 20%, surface optimization has been on by default for ages, so I leave it on and no it seems to help with DX9 apps. Both have zero performance hit. The other options change color temp, turn things on like radeon boost or chill, things that may or may not affect performance but will affect visuals. Radeon Boost is really poor because it degrades the resolution purposely in an attempt to maintain frame rate, so image quality suffers to a point where I can see it and also causes micro stutters, from my testing. Anti-lag is useless period. Your ping has more to do with lag and possibly incorrect monitor settings or not having FreeSync on. I say 20.8.3 because that was the last driver that worked pretty much flawlessly with the 5000 series GPU's. It is noted that 20.9.2 is another possible one, it really depends setup to setup but 20.8.3 is proven as "tested" for that "fix".
If your card is working as you like, leave it alone. I would suggest not using "profiles" in the "graphics" area to try to gain more than you get from using the manual fix. It winds up counter productive in the end. Your esports or whatever game will play/look the same or better than using a preset. Try it out if you want, just remember what you change so you can go back.
85c? Sounds like you might need some case airflow, like a side intake fan. You shouldn't be hitting more than 70c under full load with an undervolt as well. Unless you have the XFX THICC III Ultra or some other "partner" card with a high OC out of the box. 20.11.2 may work, nothing applies to all. The "fix" using the older driver is for those having issues. The 20.11.2 is geared more towards the 6000 series and offers no fixes for the 5000 series. In fact the 5000 series are considered EOL, so no driver moving forward will have anything new to add for a 5000 series card. The newer packages will continue to have a driver that supports the 5000 series and some older ones but nothing new. In fact if you go to AMD's main site and search for a driver for your card, you'll see they already started to separate the drivers per card series. A hint of what's to come.