It’s nice to have choices.
I just got a TC Electronic Clarity M Stereo and love it so far. It’s like adding another monitor but without taking up all the space - and with none of the usual floating window management. The ‘Balance-o-Meter’ is a triangle shaped icon on the interface that skews based on L/R audio and is really helpful at a glance. It measures phase and all the usual suspects like LUFS and can be customized to taste. I connect it using Toslink in SPDIF mode on my RME interface.
Also, SSL just released the “Pro” version of their Meter plugin and it’s on sale right now. Might be worth having a look at tto see if it would work for your needs
Thanks very much everyone for all the good advices ! Will try everything.
By the way, GainMatch works like a charm. 