RW912 - Can you please try the following tests:
Start by setting your draw distance to 3000m for all tests, then:
1. Select Kickstarter County 2 in build 100464 (Trainz Plus "live" version which hopefully you still have installed), click Edit Route and wait for it to finish loading then Exit Surveyor.
2. With the same route selected, click Edit Route again and this time, record the time until the loading screen drops. (It take 5 secs here)
3. Repeat in build 101618 (Also 5 secs here)
4. Repeat in both build with CRM Golden (30 sec in both)
5. Repeat for your route.
If the issue is limited to your route, then we need to identify what is causing the slowdown. The best way to do this is to open Content Manager and select your route, then r-click List Dependencies.
Sort the deps by status and select all Modified items, then click Content > Disable.
Exit Trainz, restart and repeat your test again. Was there any difference?
From there it is a case of re-enabling groups of content to find out the culprit item(s).
You could also monitor the game logs to see if that gives any clues (Developer > Show Logs). There is a lot of technical information in the logs but if it stick on something for a long time that could indicate a problem.