Many inverters object to voltages over 16V, so you'll be limited there.
Realistically, if you want to maximize cycle life, you'll want to operate them between 14 (3.5V/cell) and 16V (4.0V/cell).
Personally, I wouldn't use Lithium NMC for 12V. Ever. 7S for 24V, 14S for 48V.
If you made it one big 24V using only 7S, that would be more useful and present no signficiant issues with 24V inverter/charge controller.
3.5-4.05V/cell is roughly 20-80% SoC utilization for maximum cycle life.