There is no set number of points that you will lose, but it will impact your score. I wouldn't really worry too much unless you have been applied for credit more than a couple of times over the past six months to a year.
They will all run the same type of check, although they could run credit reports from different agencies. There are three major agenies (TansUnion, Equifax, and Experian). TransUnion is probably considered the leader and I would expect them all to run a TU report.
In short, I would select your service provider first and then only have 1 check run.