Agree, replace all 4 tubes and re-bias when you're changing types. Also agree the Gold Lion KT88's are great tubes. I've rolled them into my Rogue Apollo Darks and I think there's a good argument to be made they're better than the stock KT120. The GL 88's have a sweeter midrange and an overall more refined sound.
In the past I compared EH KT90 versus KT120 - the KT90 are brighter and leaner. I greatly preferred the KT120, though systems which lean a bit dark (need a lift in air and sparkle) could conceivably benefit from the KT90.
In other amps (VAC amps - not Rogue) I've compared EH KT88 versus GL KT88. Here the EH KT88 are a bit more rock 'n roll; the GL are a bit more refined and smooth. I put the Gold Lions back in, but I really like the EH 88 and keep them around for a change of flavor/pace some day. I don't think you can go wrong with any of the modern Russian KT88, and the Gold Lions are an easy general recommendation.
That sucks about the KT120 shortage - a lot of tube amp makers have been using that as a "stock" tube in their amps for a while now, and I wonder if the tooling (dating back to 2009 / 10?) is getting worn down :(