I think that you are overcomplicating the subject, and you are thinking in the wrong terms.
First and foremost, generators are not voltage producers, they are wattage producers. That is why they are rated at 500 watts, 1.5 kilowatts, 110 megawatts, etc. Yes, they select a voltage to do it at, but this is done to reduce the winding size (the amount of copper) while keeping insulation levels down to reasonable levels.
Electrical loads are also rated in watts. 25 watts, 100 watts, 1200 watts (or 1.2 kilowatts), or 25 megawatts.
Current (expressed in amps) is a mathematical ratio between watts and volts. 1200 watts is 10 amps at 120V, and 100 amps at 12V. It is extremely important for wire sizing, but is the wrong unit to think in, in a system of mixed voltages. This is why your power company bills you in watt hours or kilowatt hours, and not amp hours.
Your statement that low voltage inverters are inefficient is wrong, because you are thinking in amps, not watts. Consider the following:
System 1 12vdc/120vac, 200 watts on the 12 volt side, 10% loss delivers 180 watts on the 120 vac. You are saying 16.6 amps dc, 9 amps ac.
System 2 24vdc/120vac, 200 watts on the 24 volt side, 10% loss delivers 180 watts on the 120 vac. You are saying 8.3 amps dc, 9 amps ac. So, you think the 24v system is more efficient.
Wrong, they are equally efficient because they only lost 20 watts (heat loss) in the power conversion.
Unfortunately, we are stuck with primarily 12vdc appliances and equipment due to the automotive, marine, and RV industries. 24 or 48 vdc blenders are not common.
Our other choice of readily available appliances is 115vac (or 120vac if you prefer).
So, yes, when you try to combine the two most commonly available equipment and appliances, it can be complicated. If your 1200 watt load is a hairdryer, get rid of it and use a towel. If it is 12 100watt light bulbs, go florescent and reduce the load to about 175-200 watts for the same amount of light. Apply real energy efficiency /conservation methods to reduce the amount of generation/storage that you need. Then, when you know what your average and peak consumption is, you can design the system that you need.
For some, a 12v system is fine. With higher loads, 24 or 48 volts may be desirable and they may be more cost effective. (Smaller wire is cheaper than larger wire). But that does not mean that the higher voltage system is more efficient.