Wrong, Its the same as the 368 CPU, 32bit internal, 16bit external, The standard 68020 was the first 32Bit 68K (And even then the EC version was 24bit).
Not quite.
An Intel 80386SX has 32bit architecture, 16bit data bus, 24bit memory address (limited 16MB of ram).
An Intel 80386DX has 32bit architecture, 32bit data bus, 32bit memory address
AROS seems to run fine with these old machines.