What is a "grain weight plug?"
I have never heard of that--reason I checked the subject.
If you are talking bullets, then:
1) Most accurate--121-125gn 0.355-0.357" JHP bullets, followed closely by 121-126gn 0.356-0.358" L-SWC, followed by 112-118gn 0.356-0.358" L-SWC, followed by 115gn 0.355-0.357" JHP, followed by nothing else good enough
2) Action pistol (for less snap to recoil)--147gn L-RFN or jacketed bullet.
3) Self defense--any premium FACTORY round. I use Hydro-Shoks right now. You spend your money and take your chance. Unless they have started to do controlled shootings on living subjects, it is all guess work.