There is no B3+ as such: the AS350B3/2B1 has the Arriel 2B1, as described by Vertical Freedom, with dual (vs. single) FADEC plus backup electrical control system. Engine ratings are unchanged, but the MR RRPM range expands slightly, from 390 +4/-5 to 390 +15/-15.
B3s with dual hydraulics are also sometimes referred to as B3+s. EC still builds B3s with both the simplex and the dual hyd system, but all B3s delivered in the States are now AS350B3/2B1 configuration with dual hyd and high skid gear.
Per
this post on the AS350 thread, the use of dual hyd and high gear also allows the use of the higher 5,225 lb (vs. 4,961 lb) MTOW, which is again sometimes associated with the B3+ designation.
I/C