I'm not going to get into the PCI-slot compatibility question. There are others that I believe have addressed that. My initial reaction is that you won't have a problem. However know that I did not look at it in-depth.
Let me address though, your choice of Processor, NVMe and Memory.
You are choosing the 5900x. For about $250 more, I believe you may be better served with the 5950X. It is not for the additional 4 cores and 8 threads, but because I believe in general the silicon is better in the 5950X. All dies are meant to be 8 functioning cores. It is the Dies made from silicon where all the cores did not make the grade, that were relegated to the 5900X pool. The 5900X have two dies, where it was necessary to disable 2 cores apiece. Before making my purchase, I scoured the Internet for users and their experience with their chips. Generally I found that 5950x users had cooler chips, using less voltage.
You may also note, that in forums like this people are having more trouble with the 5900X and WHEA errors. I believe that most of those errors though, are more a fault of the users unrealistic overclocking expectations, than a fault of the 5900x.
If funds are the issue, I would suggest that you downsize your OS NVMe drive. Downsizing from 2TB's to 1TB will save you half the expense, and selecting Generation 3 over Gen 4 will save you half again. You seem to have plenty of Storage space. Do you really need it all on your OS drive? Also, it is easy to get speeds of 2500MB/sec on Gen 3. So at what price are you paying to transfer 5GB in one second instead of 2? Think of selecting your NVMe drive as a temporary option, one that will save you $300 and let you get a better processor. If there is one thing that falls faster than the price of processors, it is the price of storage.
Lastly, I can not let an opportunity like this go by without making a pitch for Error Correcting Memory. Error correcting memory has been with us for well over 50 years. It doesn't cost that much more, and it is not much slower than Non-ECC. In real life you would not notice the difference in speed. You are lucky, you haven't invested in that cheap stuff yet. However you will have all the supporting cast. The Ryzen Processor supports ECC. The X570 Chipset supports ECC, and even your Motherboard supports ECC. Don't you deserve to have your Processor check each 72-byte line fetched from the memory subsystem for integrity? Just look at the people in these forums spending Hours, Days, Weeks and even Months searching for some solution due to data corruption. ECC makes all that so much easier. It warns you of errors that you would have never noticed (check Event-Log). It corrects 1-bit errors. Unknown to most, is that ECC memory can be overclocked. The best thing about overclocking ECC, is that it will inform you (in the Event-Log) when you have pushed it too far. People who use Non-ECC can only guess. Maybe they pushed it too far, and will experience a crash later, or maybe they could have pushed it further, and they are leaving performance on the table. They will never know. All they know is that the bytes grabbed for those few hours of MemTest64 were ok, for now. Overclocking Non-ECC to me, seems as sensible as removing brakes from race cars expecting the reduced weight will make them go faster.
I get annoyed when I see Third party DIMM vendors, such as Thri-dent or X-Skill put dies on their boards spec'd 2166MHz @ 1.2V, and then expect the user to pump them up to 4000MHz with 1.4V !!!
Go Ahead, for giggles... bring up CPU-Z, open the SPD Tab, and read out the greatest JEDEC specification for your sticks. Feel taken?
My Kingston KSM32ED8/16ME or KSM26ED8/16ME have always run at least two bins higher than what they are rated for, with the application of NO additional voltage. Also the JEDEC of their dies have always been what they are rated for externally on the package.
A lot of people do not realize that the Infinity fabric clock is tied to the DIMM speed. It can be un-coupled though. The maximum speed to run the internal memory controller is 3200MHz. So running your Memory at it's advertised speed effectively overclocks your processor and voids your warrantee. Some people would have you run the memory at 3200MHz and then tighten the timings (Eg. run 3200MHz at CL16 instead of CL22). You could do that, and it would reduce the time the memory subsystem takes. However, You Know what? It is still an Overclock. You see The Timings and Voltage are part of the JEDEC specification as much as the speed.
Some things never change. Remember the Game "Hide and Go Seek"? Some kids would try to cheat and count really fast, one, two, three,......ten! Others would try to cheat and only count fewer numbers. One, two, three, four, five, six!. Either way, they didn't give their counter part enough time to store themselves away. No cheating in life.
