a) Outright cheating in the interview is probably a bad sign about the candidate (whereas the interviewers might be ok with, say, using GenAI, which is increasingly common in many sectors). But impersonating a candidate, or having a friend sit in with you, would always be a bad sign.

b) Not necessarily, some companies would care if their contract writer stole/copied/repurposed/reused content from a competitor/regurgitated copyrighted material. Think also GenAI hallucinations, fabricated citations, etc. But sure, most cost-conscious companies won't give a hoot, so they could probably get by with cutting corners.