Memtest ideally needs 6-8 passes. The more the better. 1 - 2 passes is insufficent, unless it errors out straight away. It's slow and is best to let run overnight.
P95 small FFTS mainly test your CPU Any errors, crashes here are usually due to insifficent vcore (CPU volts)
Large FFTS mainly test RAM. Any errors, crashes here are usually RAM related.
Blend (Torture Test) tests both CPU and RAM. When running Blend, you should select 'round of error checking' in the Advanced menu.
P95 ideally needs to be run 8-12hrs. Just like memtest, 1 - 2 hours is insufficient.
For both tests, only go for the 'long runs' when it has already passed the 1hr / 1 pass mark. If either test gives errors etc early on, stop and adjust. No point in a 'long run' when an error has already shown up.
Keep an eye on your temps when running p95. If it causes the temps to spike too high, stop the test. Very high temps + extended run = not good for components.