Out of all these options below which ones are most noticeable and helpful? Which ones overlap? Appreciate the advice.
Rear Sway Bar
Rear subframe tie bar
Subframe bushing collars
Diff Brace
Urethane Rear Diff Bushings

 

Rear sway bar made the most difference to me but you need a matching front sway bar. I can get on the gas harder in a turn with [Hotchkis] sway bars.
I haven’t looked at rear suspension parts in a long time, I don’t know what a "tie-bar" is.
Rear subframe collar bushings didn’t make a noticeable change to my butt or hands but after seeing Z1’s video of the dancing diff, I’m glad I added them.
Diff brace: same as subframe bushings except a slight increase in harshness.
Urethane diff bushings: same as diff brace.