I find people tend to be fairly pragmatic. Occasionally people can be dogmatic about minor things. Sometimes you have the time to do a really stellar job. Sometimes accepting some technical debt in a PR is worth it. And having that contextual conversation with your reviewer can be helpful.
If you have good tooling, e.g., auto code formatting and PR builds, the reviewer can focus on the substance of the changes, rather than more trivial things (like unnecessary spaces or new line characters in the code).
Personally, if I see a simpler way to express logic, I'll suggest it to the author. But I'm more apt to slightly-disagree-and-commit than throw up barriers, because I trust my talented, smart colleagues.
Performance is rarely discussed unless the PR's intent is to improve performance.