Both Braun and Metz generators give full power. They are in no way controlled.
The Braun generator does offer the option of half power with a special intermediate connector.
I strongly advise against modifying a Metz 45 unit.
The output of these ring flashes is modest to start with.
Maximum power is 250 WS about GN 40 with the tube fitted to the standard refelector.
Most generators will not give this kind of output.
The GN drops to 22 till about 30 with smaller generators
This ring flash is a nice option to make images with low amount of shadow.
With the diffusor it can also serve as a fill in flash. The output is reduced by 1 stop in that case.
Left to right:
Hasselblad ring flash (PK model UR 130Z), PK model 110Z
top left PK B 20 generator, adapter ring to fit 50 mm bay.
These units were produced in Köln by Paffrath & Kemper Gmbh.