for 4 XHP70.2 I would use a SIR404 FET it can handle 36.6A at 70°C ambient temperature
Bistro OTSM needs a LDO this in 17mm size adds 3$ just material cost as it is very expensive
for Modegroups can you send me the changed code, just be aware that if you use only 2 channels there are old Bistro Modegroups used
for low Vf LEDs maybe potting the AMC bank is the better solution