eccentric contractions incur the most hypertrophy but i would encourage that this is mixed with a fast concentric where appropriate, so as to maintain power. avoid superslow training! something like a 3:0:1 tempo is good for standard weight training exercises.
isometrics have their place but there is little carryover (as in, strength is only developed at, and very close to, the angle at which you are working. isometrics won’t developing strength through then full ROM).
hope this helps.
cheers.