Tyranitar as a Mewtwo Counter

Both B/SE and B/C Tyranitars are great. B/C is better for Mew and Mewtwo and has the advantage of being clearly the best dark/dark attacker. B/SE is arguably better for generalist purposes and of course against all the birds we have just fought.

In short, I don't know. I have three B/SE TTars at L30 and no B/C. I really want at least one B/C, but I have been reluctant to spend charge TM's on it.

I'd save it for Mewtwo after you catch it.

B/SE still puts out great dps i would maintain diversity and leave em as is.

I'd say have at least one B/C, psychic is a fairly common type amongst legends as you may need it for future raids too.

If you have plenty of charge TMs I would do it. I'm changing all my SE Tyras in to crunch for Mewtwo. After Mewtwo raids are over I'll change it back to SE if need be. This is what TMs are for - tailoring movesets for specific purposes.

Can you have too many Ttars? power up another one.

Try DPS calculator. SE and Cr have same dps against phsycic pokemon, but SE longer to hit.
tbh, SE is way better for generalist attacker