If you have been doing 531 for 2 years, I don’t think you are new.
AMRAP’s or PR sets are you doing OG 531?
If you are getting more than 3-5 reps on the 531 week then you should keep going.
You are not supposed to set a PR every time, just put the work in push hard have a goal try to break it.
And rest pause sets are not to be done on the main lift.
If you do FSL sets you can do 1 set of rest pause on those.