tube distortion and amp matching

for a number of years I had a CJ PV10A pre with SS amp and like anyone with tube gear I did some playing round, ended up with quite a few duds but overall the difference between a good tube and a bad tube stayed one of sound stage, dynamics and tonal fidelity . In the past year I bought a Prima Luna Integrated, wanting tube amplification and thinking that time must have bettered the PV10A (it had not). I did the same rolling with it and over time ended up with a configuration I was happy with using the PV10A into it's HT input.

Enter yesterday brand new KT-120's to replace the GL KT-88's. I decided to start with a default "safe" configuration of Mullard NOS CV4004/12AU7's to match PL's factory spec vs my 12AT7/12AU7 preferred combo. After the obligatory first few hours of break in awfulness the KT-120's opened up, were lovely and I started rolling pre/driver tubes for a few hours. As I did this the following dawned on me.

1) of the better 12AU7 tubes I had set aside in my original KT-88 configuration, all had been set aside because on some set of recordings I could hear distortion that another tube did not have
2) that the KT-120 tubes made that distortion more blatant
3) that in the CJ PV10A that distortion did not exist

Which leads me to 2 questions for those who have done this for a while with many different tube amps and the 12AU7/12AT7/12AX7 families

1) does paying for a better tube amp get you better stability with a wider range of tubes?
2) conversely of the NOS tube manufacturer's which is best behaved in the widest variety of tube amps?
Some folks say 12AU7 tubes all suck in comparison to the 12AX7 tubes. And that the only place 12AU7s are any good is as followers.. That is some hearsay I read. And I have NO idea if it is actually true...

Anyway, yeah naturally a dedicated high quality preamp is going to beat an ordinary integrated's tube pre-section!!
That is my opinion only.
Actually IMO is any high quality dedicated pre (tube or solid state) is going to beat the pre section of some midpriced integrated.
It is a lot more than ust tubes..
In my experience to #1, the complement of tubes do matter greatly, as do quality of the power supplies and especially, the quality of the output transformers.
With regard to #2, no one NOS manufacturer had a corner across the models or build configurations in terms of quality or durability. Some brands seem to be preferred over others generally, but depending on the vintage and place of manufacture, some Holland made were stellar and some were mediocre, and some German or British made tubes had mixed attributes and results, as did the US versions.
I do feel that we'll designed circuits, components and power supplies are at least as important as the best tubes put into service.