With all the LS at the moment, I decided to put my microwave on my essentials load.  In order to prevent it maxing out my inverter and tripping it though, I was considering a smart wifi plug to disconnect the microwave if my inverter exceeds a specific load [using Home Assistant].  Most of these sockets are spec'ed at 16A, but I was wondering about their surge capabilities, relay contacts etc. if I were to disconnect the microwave abruptly whilst working. Microwave has a rated input power of 1650W. I would appreciate any views on this, or to hear if someone has setup something similar to this already?

A microwave uses a 50Hz conventional step-up transformer that takes your 230V to approx 2000VAC and then uses a diode and  capacitor to double that voltage.  Note that a magnetron cannot be power regulated.  It is either on or off.  So if you adjust your microwave to 60% power, an electromechanical timer or an electronic circuit will switch the magnetron on and off at a 60% duty cycle.  Every few seconds you can hear this as the humming increases or decreases.

On microwaves with electronic displays, the switching is done by a relay.  So there should be no problem adding another relay, as long as it is rated for 15A.  A microwave draws a lot of power, but doesn't really have substantial inrush current.  (Note that EVERYTHING, including a small mains operated radio,  has a certain inrush current, as capacitors charge, elements heat, or whatever.  This is the reason why a lot of failures happen at switch-on.)

So  you can disconnect the microwave abruptly, if you don't run it at 100% it "disconnects" every minute or so anyway.