dynamic punch vs power up punch

It's somewhat tricky.

Dynamic Punch has far more damage, and a much better Damage per Energy than Power-Up Punch. PuP has low energy cost, so you can at least use it often.

If you have Counter, I *think* it's fine to give up Dynamic Punch for PuP. Ice punch is pretty necessary coverage for Medicham. The other feasible option would be to run Psycho Cut in the Fast Move, and then Dynamic Punch/Power-Up Punch. I do that with my Poliwrath (but with Bubble instead of Psycho Cut). Poliwrath's Rock Smash is weak so he can't really rely on it as much.

So yeah, you can probably swap it off if you have Counter.

It's not a clear cut. After 2 PuP it becomes equivalent to DP in terms of DPE, which makes it better because of the lower energy cost. This doesn't take into account that counter is also boosted after the first PuP. If the opponent has shields PuP is obviously better, if he doesn't DP is better imo.

It's hard to answer. If you dont have a lot of tms and dont battle a lot i would honesly just say sit on it for a month or two til we hear more feedback.