I have some experience with the transfer time, granted I have the MPP LV6548's so it might be different, but I dont actually know the differences.
I originally only had 1x LV6548, and it advertised the same 20ms transfer time. I NEVER had any equipment shut off when going back and forth. Never a light flicker, never a computer reboot, no microwave shut downs, no washer/dryer glitches. Nothing. Never noticed anything happened.
But when I got 2x LV6548's, everything changed. Now in the manual it actually states the transfer time is 50ms when in parallel. I'd assume its the same with the EG4 model. I typically had some heavy loads on the 2 of them, averaging 4-5kw continuously. My smart OLED TV never shut off or glitched, neither did the microwave of washer/dryer, the only thing I ever noticed was the air conditioners in my RV, (3x 1500w models) would slow down, and occasionally the breaker would trip, i'm guessing the voltage drop causes a big amperage spike which trips the breaker. Also, my crypto miner would reboot (highly sensitive PSU's). Nothing EVER happened when it was just 1x inverter.
I asked Ian at Watts247, and basically got the typical, "I've never heard of that happening!". His response was to reset all the settings back to default and reconfigure it, which did nothing. Never got it figured out as to why, but thankfully I don't live in the RV full time anymore, so I don't deal with the problems anymore.
@robby if you have appliances shutting down when your equipment says 10ms, I would get it tested, because I don't think its correct. Even with 50ms (probably more? no idea), i still had no problems with
most appliances.