Just tweak your tones until you like them. Then click on the output block and tweak each until levels match. Also, you have VU meters in every block now.
Normalizing volumes doesn't make any sense.
Changing any parameter in any amp is going to mess with the output.
Let's say all amps are normalized. Tweak mids. Volume changes.
And actually, even if you get them close using the VU meters, amps compress differently, so depending on how you play, one amp my sound louder than the other one.
It's just because it's the way amps are. Go play a real Twin Reverb and see for yourself.
A solution would be to disable power amp simulation and make everything linear. But for that matter, just go buy a pod xt