Yes technically anything over 25mW does require a HAM license to legally operate. Analog channels also do need to be spread out, you can usually get about 40 frequencies out of a legal 5.8ghz transmitter, however these days you can custom tune channels and define your own frequency tables through things like BetaFlight. Raceband is 8 channels spread between the legal 5.8ghz spectrum (though I think 5645 is technically not legal) and you can usually get 6-8 people up that way with decent video transmitters (many more with proper vtxs). Low quality video transmitters (vtx) bleed into other close freqencies and also make operating with others more difficult. This is also compounded by the whip antennas being used on most systems as well. A CP or omni antenna is what you want to use to help reject bouncing signals which we get a lot of on the ground. Using a higher grade vtx will not only last longer but will also work better at lower frequencies since it is tuned and designed by the top FPV company IMO. Yes I know it requires a few more wires and sometimes a solder or two but it is a WORLD of difference when you have a nice video system. It is only about $20-30 more for a proper setup versus one of those AIO cams.
Honestly what makes FPV awesome is goggles. If you can, find a friend with a pair and ask them to use it on your tank. You suddenly go from an observer to an driver and gunner at the same time. Yes you have less vision, just like the real thing! Just remember all that WIFI FPV is not the same thing as 5.8ghz FPV. They are completely different and work on a different system. If you see WIFI FPV stay away from it unless you like lag.

Clarification: 25mW is max power for 5.8ghz before Ham license needed, max 1W even with HAM license. 2.4ghz max is 100mW without license. Other stuff like 433/900/1200/1300/3300ghz all should be looked into individually.
A ham license is easy to come by just a heads up and gives you some nice max power limits. Definitely worth it IMO.