I’m assuming this will fit the C8 and many S-series lights. 8A is suitable for the SST-40 and SFT40, but will likely be limited by forward voltage with most emitters.
5A is running a 519A, SST-20, etc… fairly hard, while 3A is a pretty average single-emitter light.
Hi cri sft40? Damnit, I just built a L21B with the “new” XP-L HI with the lower Vf.