Most MTB shoes require a little trimming of the tread to clear pedals, depends on your cleat position and pedals you use.

Depends on where you order exactly - I ordered my Zeros directly from Bont, and then they are produced individually for you. I asked them if I could get a Speedplay 4-hole sole, and it was no problem whatsoever. I am pretty sure if you go down this road, they will work something out. If you plan on buying existing and standard stock from an importer, then unfortunately I don't know the answer to your question =)

Have Bont Vaypor and A few pairs of Riots for winter training. No issues using Shimano SPD-SL cleats (road)

You mention SPD cleats - I’ve not tried them on a road Bont, and don’t know if you would need the Shimano adapter plate. Sounds like a compromise increasing stack height and I would probably use a dedicated MTB shoe to avoid walking directly on the SPD cleat.

Do you mean spd mtb, or spd-sl road?

I had issues with vaypors and spd-sl cleats, as the very flat soles of the bont shoes took out the inherent curve of the shimano cleats, and brought the contact ends closer together.
Result was a very sloppy cleat/pedal.
Easily fixed by inserting a thin spacer between the cleat bolts, and giving something for the cleat to bend back around.

Hi
There are Shimano Road SPD SL cleats

The front to back curve on the base of the Bont's is flatter than the Shimano SPD-SL cleat in my experience. When you clip in you end up with a sloppy fit and tightening up the pedal spring tension makes no difference. It's possible to get the two to match by putting some bar tape across the centre of the cleat. Took me a while to figure out what was going on. It's a known issue with a thread on weightweenies.