I am an electrician and can answer your questions. I have all the festool drills and love them. The only two drills that accept the side handle are the older PDC and the newer TPC, which happens to be on the recon site now!
The TPC is twice the drill of the t-18. Maybe even 3 times. If you want to do the type of drilling you mentioned, get the TPC. The new clutch with the bind-up detection will save your arms!! It’s such an amazing drill! I used to always dread using these sized drill drivers on a ladder before I got tue TPC. Now I use it overhead with massive (6”) holesaws and don’t even blink. The safety feature is soo smooth that you don’t even feel it bind, but just hear the beep and realize that it just saved your arms!
Regarding the right angle attachments, the older style right angle adapter is the one I prefer to use. The newer unit allows you to adjust the rotation without removing the adapter. However, heavy and long auger bits or large hold saws have enough wait to cause the new style angle adapter to rotate on you when your hand just touches or bumps the adjustment ring. I was excited when they announced the new style and thought I would really benefit from the new feature, but it only took me 1/2 a day to revert to the older style right angle adapter for any drilling with more than a standard twist drills.
I also own the M18 Milwaukee hole hawg and I use this anytime I am doing a full house. However, my TPC is part of my default tool loadout and I only get the hole hawg if I’m doing enough drilling to need the extra speed that the hole hawg provides. This combo of these two drills means there isn’t anything I can’t handle.
My CXS12 is always on my tool belt. It’s also a great tool, but I don’t use it for boring unless I’m working inside of cabinets. It can handle the task of a few single studs, but doesn’t like it when you need to tackle a triple stacked stud adjacent to a window header for example. The TPC on the lowest gear has no problem with that situation.