I bought a Gigabyte AORUS 2080Ti along with an i9-9920 CPU a few months back. I bought it mostly because of the GPU power it offers to the content creation tools I use that produce PBR textures. Recently Blender announced it now supports RTX GPUs for rendering. I've checked this out in the beta Blender 2.81 and it is significantly faster than 2.80.
But, I'm not sure this carries through to the average Trainz user. Yes, you can crank up the settings and such a machine will eat it. But I find it curious that TS19 in the main menu, the one with the chosen loco, causes my GPU to dramatically increase its cooling fan speed. I wonder what is causing it.
I still believe Trainz is hamstrung by I/O. In simple terms the time it takes to load a scene. That doesn't appear to be any quicker than my previous computer. Windows is probably slowing everything down as well.
Some of the 1600 series GPUs might offer significant improvement that almost meets an RTX2080 but at a much lower cost.
If you run other games then that may be a factor.