I’m running 1 x 9 with a 32 front 34/11 rear. Do I need the long cage mech that I currently have or can I change it to a short cage or a Med one? If yes, are some better than others and are there some I should avoid?

long is usually only for a triple set up by I run it on a double without issue so yes you could use a medium or a short

as for type thatis just perosnal choice and how deep your wallett is

Suppose you could run a long cage, but med would be better and prob short the best. I have run a long cage before on my 1×9 without issue when I first swapped the front out to single ring.

Currently I’m running a Sram x7 short cage with a 1×9 setup. 32 front 36×12 rear

Zee works well for me on a 1×10, but make sure you get the right one for your cassette.

Shimano?

you’ll need a medium (GS)

SRAM

You could probably get away with a short

The reason I ask is because I currently run the SRAM XO 9 speed redwin mech and XO shifter.
And would like to fit a Bionicon v2 type chain-device and think that it won’t work properly with a long mech. Does any one have any thoughts or experienes?