Yes, you can run each one of the heated or cooled cup holders at the same time, in heated or cooling mode.
Unfortunately I need to leave the heated / cooled cup holder project incomplete. With the COVOID 19 event lowering the value on vehicles to an extreme, it was actually easier to sell our 08 Denali when it's in pristine condition and purchase an 09 Platinum ESV. Here's what's under the Platinum heated and cooled cupholder.
Nothing special except the Delphi 6 Pin female harness connector # pa6 gb20 gf10. Both the male and female are readily available online along with the timer pin connectors to make a female harness end.
Below is where the rectangular hollow air exhaust exits heated or cooled air from the each one of the TED (thermal electric device) on the passenger and drivers side of the console. It's the little plastic square grill in the carpet next to the seat.