EoL is really “end of life” and to answer your qn, just cus the rn11 is no longer supported by xiaomi doesn’t stop it from being a fantastic, inexpensive and efficient phone. you may stop getting newer features through the now missing OS updates, but let’s face it, they’re prolly gon be in the “AI” domain anyways. so EoL shouldn’t really affect you for a good couple years.
now, in case you want a fresh coat of paint, you can always just flash a custom rom on it and voilà, it should serve you for a good many more years; just keep in mind that google is kinda making life difficult for custom rom users with them going crazy over device integrity checks (there are solutions of course, just know that they take a bit of effort once in a while, and some people may not want to be bothered with it, which is when one buys a new device)

The OnePlus would be the safest bet, because its battery life would not only be much stronger (sister has one) but the network band compatibility would be more complete.

The China ROM phones would be missing a lot of important North America bands so your data speeds and coverage would be okay in the city, but probably shite anywhere else. It’s almost always better to go with the global ROM in North America unless that the China ROM version of that particular phone has most of the bands .