I'm considering buying the whole lot but I'm also wondering if its really worth it, how do they layer amongst each other
The (remastered) Cathcart timetable and the 158 timetable for Edinburgh-Glasgow basically use all the Scotrail layers. Fife Circle doesn’t for now, but will do when the mythical 158 timetable shows up.
With the 158 timetable, owning the Fife Circle route gives you drivable 170 services between Glasgow and Croy, owning Great Western Express gives you drivable HST services also between Glasgow and Croy. If you have the 380 you get some class 380 services, and of course you get 385 (the train that comes with the route originally) and 158 services. The only Scotrail train you don't get is the 314 from Catchcart, although there is 1 service for that on the base timetable. You'll also get drivable LNER Azuma services from Edinburgh to Polmont if you have East Coast Mainline.
Forgot to mention there's a Flying Scotman railtour, as well as class 385 drag moves and freight with the engineering express pack, as well as Azuma and Pendolino AI at Edinburgh
Edinburgh-Glasgow's base timetable has a railtour layer from Cathcart (cl. 314) Edinburgh-Glasgow's 158 timetable has layers from everything Cathcart's 314 timetable has no ScotRail layers but does have layers for the 66 and BR stock on Railtours Cathcart's 380 timetable has a layer for every ScotRail train in-game, as well as the Class 390, 800, Flying Scotsman, 350, etc. Fife Circle only layers in from Edinburgh-Glasgow (385), afaik. I don't own the 158 or Fife Circle so I'm going on what i've seen here. Cathcart will effectively be complete if you buy the whole lot, E-G will be good with the Sprinter.
so the 158 timetable is also gonna get a massive buff on fife too when tsw6 comes out isnt it, making it a really good value?
The Scr 158 was released for TSW4, we are playing TSW 5 now and they are saying we will get the updated timetable for TSW 6 ... See a trend here?
If you want the 158 to Fife, I advise you to wait until the timetable comes out first because as the post above said, the 158 timetable was planned for a long time and still has not been released.