To set yourself up to gain the most muscle possible, you’ll want to choose an aggressive muscle gain setting and pair this with a solid weight training program.
Time spent under progressively heavier weights will send your body the signals it needs to set your muscle-building gears into motion, and a faster muscle gain setting will maximize your ability to power through hard workouts while providing plenty of extra calories for muscle building, remodeling, and repair.
While eating more will certainly set you up for gaining more muscle, it’s important to recognize that there’s an upper limit to the amount of muscle that can be naturally built even with the largest calorie surplus and best training program. Any extra calories that are not used in this process will be stored as fat.
If you want to gain muscle at all costs, choose a fast muscle gain setting. If you want to gain muscle but are somewhat concerned about the possibility of gaining fat (which is virtually guaranteed on an aggressive muscle gain setting), you’d do best to choose a slightly slower muscle gain option.
For more info, check out The Complete Guide to Muscle Gain Programming Part 1, Part 2, and Cardio and Muscle Gain: Everything You Need to Know.