One thing that Blender does well is render an extremely high poly model and use those detailed textures on a much lower poly model.
1. Try these tutorials - https://msts.steam4me.net/tutorials/index.html#models
2. MSTS only supports a proprietary texture format - ace. While OpenRails lets you use DDS texture format. The texture basics are here: https://msts.steam4me.net/tutorials/index.html#textures
3. As Scott indicated MSTS/OR only supports textures - no bump maps, etc
4. You can use substance painter - however the MSTS texture MUST be a power of 2. And each individual texture is a separate draw call. So most models use a texture sheet like these: https://msts.steam4me.net/tutorials/...ncer/pop4.html
Chris
"True rail fans have two favorite railroads. The B&O and one other."