I have a single, dedicated layer for SC2. I didn't play WoL, non-queuing injects sounds like a nightmare!
Backspace (next base cam) inject is still a thing, but it's not really recommended: it tends to send different queens towards different hatcheries, delaying the injects. Again I didn't play WoL so I don't know which keys were re-bindable in the client at the time, but currently you can use almost anything for anything (except you can't change the modifiers like ctrl, shift, alt); those who use base cam inject will sometimes bind it to space.
Backspace (next base cam) inject is still a thing, but it's not really recommended: it tends to send different queens towards different hatcheries, delaying the injects. Again I didn't play WoL so I don't know which keys were re-bindable in the client at the time, but currently you can use almost anything for anything (except you can't change the modifiers like ctrl, shift, alt); those who use base cam inject will sometimes bind it to space.