Hi im Plymouth, but I can give you an idea,....
Yes, separate west (local) and high speed (HSS) side, if you are applying for a job it would be on the west / local side.
There are several links, the bottom link does I think Paignton, Barnstaple, Exmouth and the depot, next link up add Plymouth to that and Bristol (?), then the top two links are divided east or west, east go as far as Cardiff and west to Penzance.
If you want to transfer to high speed, they go London via westbury and Bristol, incl all diversions, Exmouth, Paignton, and penzance.
Traction wise, on the local side is 143, 153, 150, and after a time you would do 158s too. On high speed its HSTs and 57s.
Good luck.