Is there risks or limitations to install driver board under a pinball playfield?
Of course there are risks. The risks are present in any and every design project, ever. And it will definitely influence the way the system ages.

It sucks, but ultimately you have to decide how bad the situation is. The good news is you could simply decide to over engineer the whole thing and save yourself a bit of trouble taking measurements. Board stiffeners, heat sinks, shielding near operating magnetic coils, insulators  and little rubber shock mounts will solve almost any problem.

If this is a one off build, not a big deal. If you're designing a production run, then you'll want to prototype it, take measurements, and cut costs appropriately. and don't forget, there is a huge difference between cutting costs and cutting corners.