Interesting. I've used Minolta Auto 14 and Electroflash 20 flash units for macro work for decades. They're light and seem to last forever. They seem to be unique among small flash units in that they give their rated Guide Numbers. This news from my ancient Minolta Flash Meter and from GN tests with Kodachrome 25.

Neither will communicate with the camera under it.

The Auto 14 will control output in "auto" mode, gives full output in "manual" mode. It has just one output level on "auto;" the aperture to use and maximum range at which it will give correct exposure depend on the speed of the film used.

The Electroflash 20 always gives its all.

OP, its time to learn Guide Number arithmetic. For me, the clearest exposition is in A. A. Blaker's book Field Photography. Get a copy.