I believe (not 100% sure) that it's 3 range per 1 strength, if that is the correct number for example and you have 4 strength, choose it and you have an item with a throwing range of 15, it will only boost you from 12 to 15, not 18.
I wouldn't.Max range on plasma grenades is 15 hexes, so you will never be able to throw them farther than that.With 4 ST a second Heave Ho will just be a wasted perk.You ran off in NCR last night before I could talk to you more about your build.
Or 2 levels of Bonus Move, for more flexibility.(Or 2 Action Boy, I don't know if BRoF helps. 10 AG or 1 AG and Nuka Cola.)Hide behind stuff, manuever.Use Buffout for important engagements.
BROF does affect grenades.