Will 2019 27" Imac MRR12LL/A run Mojave 10.14.5, Bootcamp Assistant and allow installing of Windows 10

Harley4 wrote:

Bought this unit 1 week ago, tried to create Bootcamp partition to install Windows 10. Drive hung up and stalled during partitioning process. Got replacement unit from Apple store, (they said drive was defective), updated Mojave to 10.15 and updated Bootcamp Assistant, will this model run Windows 10? Should I use Mojave 10.16?

There is no public version of macOS which is 10.15 or 10.16.

I'm familar with Apple discontinuing support of 3T fusion drives, but what problems with 2T fusion drives, Mojave, and Bootcamp Assistant?

3T Fusion drives on 2012 models are not supported, but 2013 and later models do support them. 2T Fusion drives should work. There are known issues with Mojave and APFS Fusion on iMacs.

Can I install High Sierra instead? or is that even possible? High Sierra doesn't seem to have the problems with Fusion drives.

High Sierra cannot be installed on a Mac, which was shipped with Mojave. Mojave is the oldest macOS you can use on such a machine.