This seem like very good assembly product, but I still am confuse of usefulness.
Driver is small, this mean flashlight is small, this mean thermal capacity and heat sink is small. Because of this, at any ‘high’ drive power, led will heat up fast the most, before thermal regulation is required, then power is throttle to low. Therefore in this use case, it seem to me like there is no advantage of use two separate buck driver if the reason is to improve efficiency, because most energy loss is in led, and run time on highest mode is likely short, at most a few minute.
I only understand this concept if flashlight is bigger, and allow big sustain run time at high power. In that case, then dual buck make sense because you can use cheaper component and parallel them together. However, I don’t think efficiency is actually improve because like EasyB say, you likely use smaller cheaper component if you make two, but certain cost will be reduce.
For mcpcb, I think lexel is right. It is not advisable to run xhp70 half at a time due to thermal stress. This mean the buck need to run at same time and same power, so better to just parallel them and use regular 6V mcpcb. Less wire to led also.
However, it look like you put a lot of effort into this and I like the double stack pcb design. Good job to svitlo!