If you look over the numbers 277 Republican held seats is pretty much impossible, you'd be talking about winning around 15-20 D+4 or above seats. There aren't that many D+1 or D+2 seats in the country.
I think Republicans already hold most of the D+1/D+2 seats that exist.
I count 13 seats held by the Dems that have a Dem PVI of 2% or less ranging from 6%R to 2%D.
Yes, and the GOP currently holds 245.
245 + 13 = 258
That still leaves 19 seats the GOP would need in very Dem-leaning districts to get to 277, while not losing any of their own. That's not happening under any realistic scenario.