Regarding poor performance in SP6.
It looks like Trainz started to reduce the load on the graphics card (GPU) and processor (CPU). Hence all the stuttering / freezes / FPS drops, etc. GPU is using only 50-60% most of the time and rarely goes to and over 70%, and even if it does, just for a split-second. And CPU is even below that. I have a pic and a vid of an example attached:
This was absolutely NOT the case with SP5. The same scene played perfectly on Ultra settings on my PC: Ryzen 5 3600x (3800 MHz), RTX 3070Ti 8GB, 32 GB RAM (3200 MHz) with GPU using over 90%. Which tells me the N3V devs did this on purpose. I guess the intent was to optimize the game but it did the absolute opposite, because on high-demanding performance-wise areas (such as larger railway stations and mountains with lots of trees) you're almost
guaranteed to face this problem. I even tried to lower the settings (in-game and launcher too) to the minimum possible lever, and it still didn't work. The performance is still poor.