Most populous county to vote Republican

[Interlocutor is just not there yet]

I'm going with Riverside on this one.

Nah, I don't see Trump's margin improving much from 2016/2020 and I think DeSantis would likely do around Romney's margin here (At this juncture)

[Interlocutor is just not there yet]

No R nominee will win any of the listed SoCal counties or Clark NV unless they’re already winning the NPV. I’m also skeptical of either Don Giovanni or Ronny D outright winning Miami-Dade but would be less surprised if it happens with a D victory.

But thats the thing, a non Trump republican has a good chance of winning the NPV whether they are winning the EC or not

Republicans have fallen behind in a lot of large metropolitan areas and I think that problem will persist whether Trump is the nominee or not. So with current coalition Democrats are favored to win the PV in any competitive election. If a Republican is winning the PV then they already well pass 300+ EV. I also dont see a Republican winning the EV and losing PV happening at all unless we see some strange realingment.

I feel you are suffering from a recency bias in your assumption that it is nearly impossible that a Republican could win the popular vote in any competitive election. This is especially the case considering the apparent trends in the 2022 midterm results where Republicans dramatically over performed in NY, CA, FL, TX, etc., largely due to massive gains with Hispanics, Asians, and suburbanites in both Safe Blue States and the Sun Belt.

Much like the last time Republicans "dramatically over performed" in CA (2014), turnout was mediocre and was especially horrible in minority areas.