Update:
So far over 4k paid to engineers.
First design was slab on grade. 2070 sq ft. Shopped it around best price 23k. Plus 4k for plumbing rough in.
Oh no thank you.
So I paid for a pier and beam design and my engineer specified 25 piers. Concrete piers are around 230 each, all the way up to helical piers around $500 each.
So I'll likely go with concrete and in my estimation I'll save more then 10k compared to the slab, even after beams, joists, sheathing, and insulation etc, I'll have a foundation that doesn't move and one with easy access to repaid in the future.