Does microwave need to be an "RV" microwave?

No

No. Any MW will do as long as you can fit it in there and fake up the vents. You can drill holes and screw on the vent surround that came with the RV to any MW that size.

A microwave doesn't know where it is installed and doesn't care

Any microwave in a storm.

No, the microwave does not need to be an "RV" microwave. The so called RV units are just standard residential units that typically come equipped with external vents and baffles to route the exhaust out of the cabinet. When the 16 year old OEM Sharp microwave in our motorhome failed I replaced it with a near exact fit Hamilton Beach unit that was on sale for $88 at Walmart. The only mods I made were a couple of minor bends in the original vent mounting and small shims under the feet to get the height right in the cabinet opening. Take your tape measure with you and see what'd on the shelf at your favorite appliance store.

So far as I'm concerned, if the microwave fits with the required clearances and is anchored in the cabinet, go for it. RV specific microwaves may be built with a little higher vibration tolerance, but I have plenty of non-RV specific appliances that work just fine.

At some point I intend to measure our existing OEM microwave and the PowerXL combo microwave/air fryer. At a glance they look the same size, and if so, I plan to upgrade.