We've just spotted this post in the Systems and Security area so we are moving it to the ITSM area which is where Service Desk users should better be able to see it to respond.
I've tended to put pre-approved changes/standard changes in the main change process because often they follow a fair amount of the main flow, but skip a few steps or have slightly different assignments. Really the choice will come down to how similar your standard change process is to one of these. If they are very different, I'd make them different processes. If they are quite similar, make them one with a few branched conditions.
Just some thoughts