Nothing like the simplicity, reliability, and most importantly, the ampacity, .... of utilizing a plain ol' single pole switch!
I'm not into line voltage SSR's (solid state relays) feeding those high instantaneous current loads. so opting for simple switches is perfect. You're fine the way all the loads are divided, but there exists huge instantaneous demand possibilities. Single pole switches can pass tons, as long as all the connections are nice and snug. The sub circuits can pull 40amps off the 20amp breaker. Also, passing all that current, however briefly, thru a SSR can create subsequent choke-points and instantaneous voltage drop.
Congrats on the progress