1) If my BMR is 2000 cals, and I end up eating let's say 2300 cals. Is it possible that if I don't eat 2700 calories ( making up a theoretical optimum amount), will the calories turn into fat, because my body needed the full 700 excess calories to build muscle. so, in essence, is muscle building, an all or nothing process? If it doesn't have all the possible nutrients and cals, no muscle building will occur, or will it still occur albeit at a slower rate?
2) Say in the same vein, if I get 75 grams per day of protein on an average basis, and my theoretical optimal amount is 125 grams per day (making this number up for the scenario). by not consuming the extra 50 grams, will I still build muscle at a slower rate, or is the full 150 grams necessary for the muscle building process to occur?
1) You will still certainly build muscle, just at a slower rate than you would otherwise. You might also avoid added fat gain that often comes with bulking, so it all works out.
2) You will still certainly build muscle, just at a slower rate than you would otherwise, UNLESS you are calorie deficient, in which case your best hope is to preserve muscle while losing fat.
Main point: the body is NEVER an 'all or nothing' system.