You’re gonna have to probably pattern and see what works best on your gun. If you get too tight of a choke, it’s actually opens up the pattern.

Flight control are supposed to be the best.

I’ve always just used 00 buck (copper plated lead), but folks are using tungsten shot now with good results (but be aware the regs state it must be buckshot, slug, or single round ball, so technically you can’t do that per the law).

Finding 3.5” shells these days is tough. You will probably have to order online.

For reference with 00 buck, typically;
2.75” =9 pellets
3” = 12 pellets
3.5” = 18 pellets