I recently bought a CMMG Banshee 9mm 5.5". I am wanting to change the buffer and tube to either the KAK shorty buffer tube kit or the Maxim defense tube and stock. My end goal is to suppress it later down the line. Should i stick with the carbine buffer weight or go with something heavier? How much would a short buffer tube change the gun?

Have you shot it as it currently is configured?

Probably better of sticking with carbine weight buffer. You can add or remove weights to the CMMG bolt carrier with their weight set for a few bucks.

I have a Banshee .45. I put an LWRCI PD stock on it and I couldn’t get it to reliably run.  The short spring didn’t play well.  Spent a lot of money on HSTs tinkering with it wanting it to work.

I went back to a standard carbine spring and buffer and put I think the 2 oz weight in the bcg and it runs great with every type of ammo I throw at. Cheap ammo to 230gr hst(Rugged Obsidian suppressor)

Obviously.45 is a bit different , YMMV

They made my 9mm RDB bouncy.

I was getting trigger slap with 9mm RDB upper, RR, and Kynshot 9mm buffer. It was really bad with WWB 124 gr and let up a little with heavier subsonic ammo. The medium CMMG action tuning weight smoothed it out.