Would I still be able to open the switches, when glued?
You couldn't open them anyway, because the tabs that holds the switch together need to move and those are restricted by a standard 14×14 mm plate hole. Only enthusiast-made plates with special cutouts for those tabs allow switches to be opened while mounted.
These tabs are on east and west sides, while the snaps that would snap the switch in the plate are on the north and south sides.
From what I have seen, most builders that hand-wire switches use hot glue on the north and south which would not interfere with the tabs on the east and west sides.
I'm not a fan of hot glue so I have not tried it but I have heard that it could be pried off more easily if alcohol is applied. Be very aware that alcohol could also dissolve paint and lubrication, though ...
I have found an alternative to glue, but it works only for plates with cutouts... Open the switch, mount the bottom into the plate, insert a small piece of plastic card into the diode-slot and reassemble the switch. If the card is of the right size and thickness, it will prevent the snap on that side of the switch from opening and thus prevent the switch from being pulled - fully
. The snap on the opposite side can still unsnap from the plate.