Would not use foam core unless you are going small. Many non businesses still use it for its ease of cutting and cost.
We used to mount small canvases to foam core (Under 16x20) but no longer use any foam core.
Too easy to dent and bend. 100% gatorboard, even for the small pieces.
We use Miracle Muck but also mount a lot of canvas through our laminator using Seals Print Mount Ultra.