Sea of Green: focusses on a singular main colas growing them as big as possible with preferbly no side branching. The area to grow is maximized by placing as many plants in relative small pots as possible. No screen is used.
Screen of Green: focusses on side branch distribution to an as wide area as possible to maximize the grow area filling it out with only a few plants in big pots. The screen is used here to tie down larger growing bud sites to try and keep them all at the same height and keeping the light as close as possible without burning any bud sites.
12/12 : is just a light on light off schedule. has nothing to do with SoG or Scrog, apart from it being the default flowering schedule.
In order to go in for 80 days, you need to flower asap, relative short vegetation. Asssuming an aprox 8 weeks flowering periode, you have just about two weeks for vegetive phase, Might be an idea to adopt the 18/6 light schedule during those 2 weeks vegetive state, just to get the little plants to stretch as far as possible before you flip them to 12/12. What I would recommend is doing a 24 or 36 hours dark periode to kick start the blooming before you take on the 12/12 schedule.
Possible issue: your plants may not be done flowering in 80 days if its a 8+ weeks flowering plant/strain.