HRC's faithless electors were just a useless political ploy, if she had won a narrow majority you can bet that all of them would have been lockstep in supporting her.
I do sometimes consider a situation with a 269-269 Electoral College tie, where one elector defects to the national popular vote winner to give him/her a 270-268 majority. I do think a partisan elector could be motivated to believe that outcome is preferable to an election decided by the House.
I'm not sure latter could happen. A Dem elector voting for a GOPer like Kasich (if he won the NPV) wouldn't surprise me that much, but vise versa? I dunno. Maybe a traditional conservative voting for Biden over Trump in such a scenario. But if 2020 ended in a tie, pressure on electors of both sides would be extremely high not to defect from their party.