It has a minimum rating (0), and you will gain/lose a maximum of 10 points
You don't always get +/- 10 points. Depends how many games you've played on templates. For the first 30-50 games, it's +/- 10 then the win/loss points are always less than 10.
2) no but you can check people's QM rating and rank in the QM leaderboards for players with a rating of 200+.
3) I've done an experiment with this before. Tried to play only 1 template for a month or two in real-time only. I found that all matches up to first rating up to 350 where quite inaccurate. From then onwards, the matches were very close and winning a game increases you rank slightly and losing a game reduces you rating significantly. Now when I try to play games on certain QM templates, I'm very likely to loose due to the early match inaccuracies. When I started, my average win streak was 7, highest being 10.
Tldr; in the short term yes, mid term no, long term doesn't matter.