No cbd doesn't negate thc's effects, and I too once lived on shwagg weed and when I finally started growing back in 2002, my views of "good weed" changed forever.
First of all, don't buy the Fox news bull jazz about medical grade weed being some scary bad drug. Instead of having to smoke a whole joint of crap weed to catch a buzz, you'll only need two hits of some 15%+ thc weed. Yes, if you sit a try to smoke good weed like it was shwagg then you're going to get way too baked, so moderation is key.
I think for your needs some of the cbd strains or 1 to 1 ratio strains are going to be the best thing. Some less potent strains I know off hand are big bud from any breeder; orange bud, fraisin dew from dutch passion's, almost any purple strain.
Just stay away from the og kush, jack herer, hash plants if you don't want really high thc ratio.