I'm going to make a route for all types of traction and wanted to know what the best looking tracks with 3rd rails are or if there is a 3rd rail spline
There are a number of 3rd rail tracks available(e.g kuid:87487:*****, kuid2:121826:*****:*) as well as stand-alone 3rd rail splines. The kuid2:121826 range are the U-Bahn range, high-poly and scripted but very nice.
Bear in mind that 3rd rail protocols vary - some (e.g. in UK) have the train conductor shoe running along the top of the rail. Others have the conductor shoe coming in from the side, and some have the conductor shoe contacting the lower surface. Then there are cover boards. Some over the top of the conductor rail, and some over the top and one side - and some none at all.
Also, some 3rd rail systems use a 4th rail as the neutral conductor (in the middle of the rack) - though they are still regarded as 3rd rail systems.
Doing a route combining 3rd rail and pantographs will, in my experience, be very demanding (albeit hardly prototypical). Junctions and crossovers can be tricky with 3rd rail track, but done properly they look terrific. When laying 3rd rail track, you have to keep in mind that the conductor rail cannot be featured on one side of the track for long distances, otherwise the conductor shoe would overheat - so, having decided on a track, you need to lay it in one direction, then another so that the conductor rail switches from one side to the other and then back again.
