Question: FF DoF vs APS-C

It's actually very simple Depth of field for any format is directly and physically related to Distance, Focal length and defined circle of confusion . The last bit can be defined mathematically but it usually lives up to its name and ends up in confusion because it involves opinions perception of out of focus blur to arrive at a number.

Basically change aperture or focal length to taste. If your taste is an eyelash DOF then full frame and a 200mm f0.95 may be what's needed. However a bit of photoshop blur filter could be slightly cheaper.

Did PR  series this week 30mm F1.4 full open on the Pentax because the D700 had a broken 35mm F2