I use a RT4k on a 65" OLED G4. games from 16bit consoles can look really really good, especially if you turn on HDR in the Tink settings, it really helps with the dimmer picture when using simulated scanlines.
Beam emulation, and other fancy options are all good too, but no matter what I do or enable, it really isn't the same as a CRT.
games that switch resolutions, will sometimes trip up the RT4K and produce some weird artefacts or strange behaviour
sometimes you'll spend more time fiddling with settings than actually playing the game.
Depending on your consoles, you might find other weird picture issues being amplified at 4k, like Jailbars or other noise in the analogue signals etc
at the end of the day its a step closer and using HDMI out from a mister and into the Tink can produce some unbelievably clear images but motion clarity and overall feel, just doesn't convince me its the same as playing on a real CRT.
I have multiple cabs, and a bunch of CRT monitors and the CRT's always win I get the most fun playing on a 14" Philips monitor, not even high end!
But if you really need to play on a larger TV that needs a scaler then RT4K is the best at the moment.