QNX DR Concurrent CPM which became Concurrent DOS DR FlexOS PC-MOS
I seem to recall seeing a few others advertised in magazines at the time.
As to DESQview, it had DESQview/X as an addition.
As to unique bits, what OS/2 had was memory protection, but then so did QNX and FlexOS, I'm not sure about PC-MOS.
QNX DR Concurrent CPM which became Concurrent DOS DR FlexOS PC-MOS
I seem to recall seeing a few others advertised in magazines at the time.
As to DESQview, it had DESQview/X as an addition.
As to unique bits, what OS/2 had was memory protection, but then so did QNX and FlexOS, I'm not sure about PC-MOS.