The control’s position before any post-effects is important to prevent it cutting-off delay and reverb tails, etc. If you want a pedal-controlled volume elsewhere in the signal chain, you can do this by putting the pedal into ‘expression’ mode and assigning it to control the ‘level’ (or similar) parameter of one of the other effects in the chain.
I’m going to be getting one of these pedals for Christmas for my Mustang III amp. A friend bought the EXP-1 pedal a few months ago. He use it everyday with his Stage One guitar and Mustang III amp. So far he’s been very happy with the pedal. It feels and sounds good and it’s totally quiet. The EXP-1 in volume mode adds an additional volume control in the signal chain, after the amp model and before any post-effects. The exp 1 volume mode settings are ‘global’ across all presets – unlike the EXP-1’s expression mode settings which are specific to each preset.
If you don’t have the EXP-1, this (conceptual) volume control is always set to maximum (as determined by the preset volume, the master volume, etc). So the EXP-1 lets you go from zero to that maximum, but won’t override the maximum already established from the other controls.