Having not experienced the usage of GMRS as much as I would like I can say narrowband MXT400 works well with many other radio's I run with in a pack of about thirty. My only issue is that I have to turn up the volume occasionally for the wideband signals.
It seems the new users in a pack might get excited and try to talk over others at times creating a mess with signals out in the woods and mountains but, other than that, everyone sounds clear as a bell in my Jeep.
It's still ladies to the right and men to the left, where I come from.