Basically because you have overclocked your RAM then you will need to run memtest86 at bootup. If you don't make sure that your RAM is good to go then as sizzling says you could pass stress test but still get issues. You still after a minimum of 32 of each test 0-9, 8 passes test 10 and 16 test 13. You need to run each test all at once or its pointless. Test 7 needs to be run 32 passes because that gives you full coverage. You will feel the pain of failure 24 passes into the 32 pass tests but once you are stable it makes the other tests more likely to pass.
Prime95 is another good test but you have to enable all the error checking or its pointless. This is mainly for testing the cores. How you run prime 95 is up to you. 10 hours of 8k ffts and 10 hours of max ffts, should do the trick for games. With Aida64 just run for +12hours. If your cpu gets too hold with AVX instructions then you need to dial back the overclock. Being stable means any load should be fine.
Some HEVC loads are maximum power and heat just like prime95. Core i9 9900KS @ 5.1GHz HEVC Power Consumption 365W / Core i9 9900KS @ 5.0GHz HEVC Power Consumption 355W / Core i9 9900KS @ 5.0GHz (MCE off) HEVC Power Consumption 254W / Core i9 9900K @ 4.7GHz HEVC Power Consumption 289W.
https://www.eurogamer.net/articles/digitalfoundry-2019-intel-core-i9-9900ks-review
Now run some games and see if you are stable. Watch videos on youtube and visit the websites you like. Transfer data between drives and see if it becomes corrupt.
Once you believe the core part of your system is stable then move onto the graphics card. I have found Control is good for the cores overclock on my RTX 2080. World of Tanks EnCore RT is great for RAM stability on my RTX 2080. Every load is different on a graphics card and what settings are stable change from game to game.
Control required the lowest core overclock and World of Tanks EnCore RT required the lowest vRAM frequency.