Me too 
It wasn’t until I read your answer I understood we were talking USB cables, and I’m an IT guy.
I’m old enough to have used time resoldering pins of cables back in the days when different manufacturers hadn’t yet quite agreed on the cabling standards
I think I came to a consensus.
I bought an 88 key controller and one 61 key controller for the top. (Komplete Kontrol s88 mk3 and the Korg Keystage 61).
I also like the fact that the Keystage doubles as an audio Interface (with a l/mono output, rare for an audio interface) eliminating the need for me to need to add extra components (although I do have a Scarlett 4i4 gen 3 just in case things go wrong).
I did a rehearsal with one 88 key and some things did feel a bit difficult but it was mainly getting used to the split performances. With a 88 key board you still have to do jumps, just longer horizontal ones vs. vertical ones. Both take some getting used to I guess but I think I am more used to the vertical jumps with my style of playing multiple parts and with the right programming I should be able to play a bunch of parts with one long 88 + a 61 key synth action (all with practice).
There are still a few kinks I have to deal with but my setup will mainly consist of
A two tier column based keyboard stand (Komplete kontrol put all of their important external connections in the middle of the board making this a bit of a pain). But otherwise compact, sturdy and farily quick to setup.
Komplete Kontrol mk3 s88 (solid build otherwise, Weigthed keys, a bit firm but fairly smooth action, smoother than the Kronos).
Keystage 61. (very light action, very light keyboard, a bit lighter than I’m used to with the Montage M but very workable and still a premium feeling). Will be the audio interface. (also great that the audio interface total output is right on the top of keyboard making it very easy to control overall volume. Also have a laptop holder which IMO doesn’t feel sturdy enough for a Macbook Pro, but perfectly fine for a Novation Launch Kontrol XT)
Novation Launch Kontrol XT (to change sounds/ mix volumes etc, any random controls I need for certain songs). (still need to get used to some things though)
Macbook Pro M3 (pretty powerful, there is a bug with Kontakt that crashes PC, but I believe latest update might have resolved it. Only three USB4/Thunderbolt ports. I’m thinking though just using all three I shouldn’t need a hub which would add another point of failure). I will need spare USB cables though.
Samson Laptop stand. Very easy to setup. I’m debating on whether I should keep the “sticky” padding though as it looks like it would make it hard to remove laptop after a long gig,
EV8 Pa speaker (for keyboard amp)
Duffel bag with cables and miscellaneous stuff that comes handy from doing gigs over years.
That said I didn’t think it would be that much stuff to think about getting into all of this (other than Gig Performer itself) (e.g 2 vs one keyboard, laptop stands, location of usb ports on the back of controller), but I think once everything is setup, should be a fairly smooth process.
Nice set up.
As written before, for lead singing and keys the second board was to „high” for me.
We run the whole band through GP, as Audio Interface and Mixer we use the Behringer XR18.
I build a high performance win desktop pc and have a 16 inch touch monitor in front of me.
I control all with my keyboard (SL88 grand) a Behringer x-touch mini and the touch monitor in front of me.
Since using GP the band lost a lot of weight…
Thanks to the GP team!