Republicans supposed "disadvantage" in the popular vote is oversold. Any plausible Republican nominee *not named Donald Trump would have won the popular vote against Hillary Clinton in 2016, and said Republican would have probably been reelected (with a popular vote mandate) in 2020.
LOL no.
The GOP has only won the popular vote once in the past 30 years. That one time in 2004 was mainly due to the rally-around-the-flag effect and incumbency advantage for Bush 43.
Until the GOP can appeal to urban areas more, no GOP candidate is winning the popular vote in the foreseeable future (unless a Democratic presidential candidate has some extreme scandal against them).