different aux switch/ex pedal per preset?

The expression pedal programming is per preset, but the aux switch programming is global.  The one exception to this is for Space algorithms where you can use the HotSwitch functionality to create different parameter value positions in a preset which can be toggled with an aux switch (or the performance switch on Space).

You might want to try using the expression pedal mapping functionality instead of the aux switch if you want your control to be preset specific.

Depends on what you are trying to do, but consider that if you setup your aux switch as if it were a pedal, the stompbox will not see a difference, and you can then use the switch to control parameters on a per-preset basis.