In my experience, PC Matic does a good job with optimization. I don't know if it's literally the best security program but it seems pretty good. I did run into problems before but it was when I installed third party software from other sources than the people who made it.
If you are installing third party software and you get a menu asking you to install a bunch of extra stuff that has nothing to do with it, it's a warning. Don't do it!
If you are installing third party software and you get a menu asking you to install a bunch of extra stuff that has nothing to do with it, it's a warning. Don't do it!