I used a 150w portable MSW for a while. It put lines on the tv and the bricks seemed to run hotter than at home. At times I had a gaggle of items plugged in with an extension cord for more outlets and draped over to the table at times for use. No actual harm to anything.
Now 300w PSW GoPower wired into the existing outlets works way better for us. Far more convenient, no electric noise on the movie screen, no set up-just touch the remote for instant power, and the brick(s) seem to run cooler. On one trip my fridge did not light so I was able to use the inverter to keep it running in transit. I was able to repair the fridge after arriving at camp.
Still carry the old inverter. Have loaned it out twice.
Mine is wired in behind the electric panel. 12v power from the main battery feed. 120v connected to two branch circuits with transfer switches.
BTW 300w will not run a microwave.