Flat - Race Face Chester on my fatbike and a similar form giant on my hybrid.
they keep my feet on, i literally have to lift my foot to move it around, that is how good they hold my feet.

I'm cheap and just use whatever shoes I have. For example, I have old tennis shoes not good enough for walking (hurt my feet), but they are fine on the bike. That also is more practical than having separate biking shoes. And if you ride through the seasons you need quite a lot of bike shoes and boots if you have clipless. I just use my super-insulated bulky winterboots.

I never used clipless, so I may not know what I'm missing. But everyone I know with clipless fell at least once. and with a fatbike going through mud, sand, snow etc. I imagine you need to take down your foot more often than with a road bike. i know many MTB people have clipless, but many winners of MTB races also have flat pedals.