The Ryzen 5 5600X requires a CPU Cooler rated 65 Watts or above and has a Maximum Operating Temperature of 95C.
Both the 1600 and 5600X are rated TDP 65 Watts and both are bundled with the weakest AMD CPU Cooler, the Wraith Stealth.
I suggest you try and see if the current AIO you have will keep the Ryzen 5600X at or below 85C under stress or heavy loads. If not, then you probably will need to install a stronger AIO or Air CPU Cooler.
Seems like many Review sites about the Best CPU Coolers tend to have AIO with 280MM Radiators on them. Here is an example: https://www.bestgamingreviews.com/best-cpu-cooler-for-ryzen-5-5600x/
Okay, how long should I run say, Cinebinch R23 to determine my cooler can handle it? I ran a single Cinebench R23 render and it only got to °61.
In my opinion, if the CPU didn't go over 85C under stress for 2-3 minutes and the hottest it got was 61C which is excellent then your AIO is sufficient enough for the processor.
I have a Ryzen 3700X with the same TDP of 65 watts using a Cooler Master Hyper212-EVO cooler with 2 fans and the hottest it gets is 71-72C.
If the AIO you have was not strong enough the CPU temperature would have probably spiked past 90C very quickly.
I use OCCT CPU Test with Small Packets and extreme settings to test my CPU Cooler. I make sure under GLOBAL TEMPERATURE setting I inputted 90C to stop the test if the temperature reaches 90C during the test or you can use some other Stress testing program like CPU-Z stress test your CPU also.