#1
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.
#2
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