Is there a way to disable or shut off routes. I recently added a couple of routes,and it kind of pushed me over the edge,loading and framerates went very low. I'm new to TSW2 and not completely sure how things work yet. Maybe a new route folder or a second installation of TSW2/
Through Steam (assuming you're using Steam), you can uninstall DLC if you don't use/want it. Scroll down and click the 'Manage my DLC' button, and untick the ones you don't want. However, you'll have to redownload and reinstall them (same method) if you want to use them again.
You could use Clumsy's method or you could highlight Train Sim World 2 in your Steam library and then right click and go to properties. Then go to local files and click browse which will bring up your TSW 2 installation folder. Double click Windows no editor, then TS2 Prototype, content folder, and finally the DLC folder. You should now see all your installed routes and trains etc. Select the content you don't want for now and cut and paste them somewhere safe outside of the DLC folder. When you need them again simply cut and paste them back into the DLC directory. It may sound a little confusing at first but it's very simple once you have done it a couple of times. This will save having to install them again.
Issue with that technique is every update will cause them to be reinstalled. I've done that method with Bakerloo (which you can't officially uninstall) and it's a PIA every update if I don't remember to move it back
Not true for DLC in my experience - I've moved Reisa-Dresden out of my DLC folder and it's not re-appeared (I don't think there's been any updates to that route since, though). Maybe it's because Bakerloo is part of the base game but I'd have thought it'd only put it back if that item was being updated.
Sadly not any core update reinstalls Bakerloo, like you say Riesa Dresden should only get reinstall if there's an update to the route.
It's easy to do - but having routes installed shouldn't affect your framerates in any way. The game only loads the route you are driving; the rest sit passively on your HD or SSD. Something else is causing the problem (possibly the route itself; the routes released from Rush Hour onward definitely are more challenging for hardware than the older ones).