I’ve used a finalizer pretty extensively in studio mastering situations & there’s no doubt with careful setup it can make a remarkable difference.
I know an engineer who runs one live & personally I don’t think it works, well not for him anyway lol. Not tried it myself live however, maybe I should.
I think for a live show where you’re supplying only Left & Right, if you had your own engineer & time to soundcheck properly, it could make a noticeable difference.
Without an engineer/decent soundcheck I think you could end up in a big mess pretty quickly. Not trying to put you off, I’m all for experimenting, but I’d use it with caution 