In your case, you can provide the isolation for each appliance using
any of: 20A double-pole switches,

not on a 30A circuit though.

Why not?

If the 3.6kW is a maximum load, then the switch won't be asked to break more
than 15A. I suppose you could argue that "nature of the load" arguments
don't apply to microwaves.

OTOH, I'd probably just install a 45A DP switch anyway.

Christian.