Can Unity Achieve Realistic Rendering for a 3D Room Design Tool on Mid-High Range Mobile Devices?

It’s feasible on URP.

The problem is if you want dynamic bounce lighting, that would require SSGI of some form.

Either kronnects solution or the opensource solution posted here. Note SSGI can be heavy on mobile devices, just depends.

Couple this with APV if you want time of day and it should look good. But much if it is knowing how to render things in a game, good light settings and such.