Multilevel inverter question
Multilevel inverters is efficient (just google random 10 science articles about it). Instead, they have much more complex control logic. You've chose H-bridge based topology - it's good, but expensive. Look at diode-clamped ML inverter, maybe it's enough for your purposes?

For PV converter you better look for "multilevel inverters for PV applications", they're a bit different. For example, just one inverter may be not enough, most solutions i've met in articles uses additional boost converter on inverter's input.