This is Matt, the creator of Trainyard. @DMGregory summoned me here! :)
It sounds like you're working through the same issues I had to deal with. It's a tricky problem where there isn't necessarily a perfect solution.
One thing to consider is the constraints of the problem. I was targeting a 50mm wide screen on the early iPhones, and Apple's recommendation ...
I think you can solve the two pain points you indicated with a few heuristics.
One is a little hysteresis: once the player is drawing in a particular row/column, keep their drawing cursor locked in that row/column until their mouse/touch point strays more than ~30% of the way into the next row/column.
That gives more tolerance for error, so the player has ...
The obvious ones are:
Maximum LOD level (if using LOD models)
Shader quality (if your engine supports adjustable shader quality)
Max particles onscreen
Profiling is a good way to determine bottlenecks, but if you're profiling on a high-end development rig and worried about how ...
For keyboard inputs, a simple but effective implementation is to have a set of keys that when repeatably pressed, change the player's orientation by rotating through the surrounding tiles in a clockwise or counter-wise direction.
So you could set the 'A' and left arrow keys to cycle through adjacent cells in a counter-clockwise direction and the 'D' and ...
Found some interesting discussions of this question, one that pointed to the following podcast at 43:35. The most salient point, in my opinion: "[remapping controls] is a bug factory".
My suspicion would be that in reality it's not that the limitation of consoles prevent these sorts of custom settings but rather that the variability of PC ...
I would suggest that if your testers found it difficult to draw track shapes they wanted, this may have to do specifically with your using a 4-connected grid (of a certain coarseness of resolution).
Have you considered:
increasing the resolution of the grid, a finer grid giving the player more control over how the track is drawn, while keeping the tracks ...