I precached my content and defragged my old platter hard disk where my content currently resides and that really helped a lot. I'm looking at a 4 TB SSD, but my budget is telling me not to do it right now.
To precache your content:
Ensure that advanced debug tools are enabled in Trainz Settings. It's a checkbox located under the Dev tab.
Click on Developer on the top menu bar and then click on Run TrainzUtil command...
Two bars will appear. One is the activity log and the other one you type your command in.
In the command box, type prebuild.
Notes:
If you have a lot of installed content, this can take a very long time. I recommend letting the process run overnight undisturbed.
You may see some errors in the log. I noticed they don't seem to do anything.