Are you putting LED's in the panel or the garage?
The type of load you have is non linear in nature, but you still can use multiwire circuits for non linear loads - you just need to consider them to be current carrying and not simply carrying unbalanced current. If the source is from a wye transformer (which 208/120 will be) then you still consider the neutral to be current carrying if the circuit in question is only two phase conductors and a neutral whether you have non linear loads or not.