6 awg is good for 60A fuse (I use it for 70A)
10 awg is good for 30A.
If more than 3 current-carrying conductors in cable or conduit, then there is derating to lower current allowed.
Also if in hotter than normal environment.
Hot "Line" wires count as current-carrying. Ground does not, and neutral in split-phase 120/240V does not.
Because 10 awg has 40A ampacity (although no larger than 30A fuse allowed), even though you have 4 hot wires going to two inverters, the derating still allows 30A fuse.
Your drawing shows two separate 30A disconnects (fused?) after the breaker panel with 30A breakers.
Utility may want a visible-blade disconnect, to be absolutely certain power source is isolated.
But do they require a single switch, rather than two separate ones? I don't know.
Mine has a single switch, branching to multiple breakers downstream.
You could put a single switch before the sub-panel. Which of course means any loads there would be shut off at the same time.
Or a single 2-pole breaker in the panel, feeding a 60A switch, and multiple branches of fuses/breakers downstream (like I did.)