Assuming you are talking lvl 75 builds I expect that is still being figured out.

What I have figured out is our builds will be slightly different depending on if we bolstered or not. The decision to leave the old FPs and ops at lvl 70 and nerfing our characters to that level was not very bright as it greatly limits our build.

Stims that increase max endurance, mastery, and power are only useful if we are not bolstered down to lvl 70 as the bolster system determines those numbers based on our gear quality. Relics that proc power and Mastery (and probably provide power on use) are similarly as useless . This should also apply to all sets that provide max endurance and max mastery. I have tested The Entertainer set and saw no difference while in combat.

% is not affected by bolster. That includes Crit chance, alacrity and accuracy. So DPS would still benefit from the Proficient Stim. Ironically, this means the relic that procs crit is the most useful when bolstered down to lvl 70. The other relic slot is just for any lvl 306 for gear rating purposes.

All those items would work when not bolstered. The new FP and operation should not bolster us. Though I will say the bolster system is rather broken as I have seen cases where we were some members of a MM FP group were not bolstered.

TLDR, save all relics that proc mastery, power, and crit for now. Use Crit proc relic when bolstered down to lvl 70. Proficient stim is good in all environments. And of course no build info from me in this post.