When I see all those full stacks on the stages, I ask my self: are they connected to each other?

Nuno Bettencourt used to have a Hughes & Kettner Triamp for rhythms and a Marshall JMP for solos, but is the Marshall just like an overdrive on the H&K or is totally separete? like using a ABY pedal.

If you have any comments about the gear of any famous guitarist you can mention about it.
the JMP preamp is used to change the sound by boosting the HK amp in a way the guy likes.

unless the guitarists name is yngvie its just about guaranteed that not all cabs are connected- dummy cabs with no speakers.
'87 Fender Strat
Oscar Schmidt Archtop
Laney LC15R