Bake those substances
Substance painter is a very powerful tool, but it has downsides. I did...let's call it "unpaid work" for "an organization" that saw that the substance code was smaller (file size) than the baked texture files and thought it was an optimization because of fanciful notions about bandwidth and hosting. Six months later I joined and was tasked with figuring out why it took the game 30 minutes to change scenes (or start, as you're seeing).
They also wanted to use one material for everything because the artists wanted to do all of their work inside Unity rather than in substance painter just by fiddling with properties in the inspector. And wanted all of the tools substance painted offered.
Rather than exporting the material properties of your substance, bake it down into a texture or two. Also, you seem to be planning for mobile devices, where my advice is: don't use substance painter at all. Mobile devices do not have the cpu, gpu, and ram necessary to handle complex materials (heck, most mobile shaders don't even offer color multipliers). You need to think about batching, both static and dynamic and complex materials will almost certainly break batching. Especially if they are procedurally generated.