It's good to know the problems you had -- unfortunate you had to have that experience, but good for others to be warned beforehand.
McAfee, like several other brands, has it's own special removal tool https://service.mcafee.com/FAQDocument.aspx?id=TS101331
Security software digs itself so deep into Windows that as you said, it's Very hard to get rid of otherwise. If it helps anyone in the future, to disable Bitdefender &/or Kaspersky I've booted to Safe Mode, where I could disable their services, at the same time removing them from the registry's run keys.
Bitdefender 2014 has/had a game mode you could turn on -- it's missing in their 2015 version, which is why I haven't upgraded, though I'm sure I should, assuming the newer version does a better job. I know the AVG free software lets you disable real time scanning, because I disable it to speed up my before/after snapshots in my XP Mode VM.
Right now I have McAfee because of a deal where I bought a 240GB SSD + McAfee, & got all but ~$25 back via MIR. Part of the deal was I had to install it & sign up for auto-renewal for 11 months. I installed it to the more-or-less backup copy of 7 I've got on here in place of my old XP Pro install.
Don't use it but a couple few times a month, but it *seemed* all right, so used it to replace Bitdefender on the copy of Vista on my wife's PC [she mainly uses 7, but has Real Arcade games in Vista she can't switch over]. Bitdefender gave Vista fits when it started up -- McAfee doesn't. I thought: Cool!, & stuck it on my bargain basement Windows tablet, where it seems OK [Knock Wood]. I know it's not the best, but if/when the better stuff won't run, Oh Well...
