Hi,
I use MPC live 2 and some elektron boxes, but I mostly use them separately. There are benefits to having both if you like the MPC workflow.
I don’t think Live 3 can use an audio interface while simultaneously maintaining it’s own internal I/O which includes the built-in speaker (so probably audio over USB either). You’d probably have to monitor from the elektron box to use class compliant audio over USB (because it serves the function of an audio interface, or technically is one). That means anything physically plugged into MPC analog inputs or outputs at the time will not work.
If you visit the MPC topic, you’ll find some people already using these devices together and may have some better perspective.
Linear / timeline sequencing and audio recording is useful. CV sequencing is very useful. Battery life is said to be poor on Live 3 but may not concern you in a studio setting. Touch screens on MPC devices kinda suck but it’s useable. Best sample chop in the game.
Might get a different perspective from someone else but you may end up like me where you work in one box and then work in the other separately, probably with resampling.
The MPC sequencer doesn’t feel like the elektron sequencer. It’s just different. Sometimes I have to get off the MPC to execute an idea on digitakt or digitone because it will be a lot easier than to make the same thing happen on MPC, sometimes the situation is reversed.
I think it will be hard for you to decide without trying the MPC, preferably in person before purchase.
Good luck