I'd bet (c) the M* variants offer the same generation of CPU in devices like the Mac mini but with more cores, a higher power budget, and less restriction on the code you can run. The A20 Pro just hit Geekbench first, both the A20 Pro and the M6 start shipping this month.

Edit: Looks like a believable M6 result appeared just this morning https://browser.geekbench.com/v7/cpu/354109 ~1.02x single thread & 1.99x multi thread vs the A20 Pro