Expanding two gang box to three gang with metal conduit
The conduits will bend even if rigid, if thin wall or emt they are easily bent into place.
I pull my wiring out and mark with a paint pen or sharpie stripes take a picture or draw a schematic black wire 1 has 1 stripe white wire 1 has 1. Red 1 has 1 then black 2 has 2 etc.  normally not more than 5 in a box keeps from having so many stripes).
Power off of corse. Disconnect switches, pull nuts, remove fasteners(screws or nails) fit wires and conduit into new box install locknuts /bushings if needed. Anchor usually with screws install switches.
A small pry bar or wonder bar can be a lifesaver muscling the conduit.
try to not skin the wires if you do skin them the world is not over some shrink tubing will fix a skinned bit of insulation.
I have done jobs with rigid a foot up in the wall it was anchored but I could get the conduit into the box with a bit of brute force.