Synonymous with the word "swag" by strict definition. However, "sweg" is typically used when a person is trying to differentiate themselves from those who have supposedly have "swag". It is also used as a humorous variant, as if saying (or "having") swag doesn't already make you look like a joke.
Sweg is also used extensively by the YouTube character Spodermen. In that video series, the character (Spodermen) supposedly has sweg, and most other people don't (they are "fagits" automatically) but are still fagits even if they do have "sweg" (because "only spodermen cen have sweg an nawt be an fagit")
Most people will correct your spelling if you use it, assuming you meant to type an A.
Slimy Wet Evangelical Grin: the stupid smug look of spiritual bliss that is supposed to tell everyone that you think that your imaginary friend called Jesus is real and talks to you and will save you from getting genital warts if you fuck the minister's daughter and say sorry to him (Jesus) afterward.
It also apparently allows you to wax lyrical about any topic on the planet with divine authority and irritate the shit out of people within 400 nautical miles of where you are.
That idiot over there should take his bible and shove it up his arse - that will give him a proper excuse for having that dumb-arse SWEG on his face