My 325i (e36) as well as my 528e, in good company with my 84 Vanagon all use
1157 bulbs which are 21 watts for the brake lights and 4 watts  for the
running lights.See page 97 in your owners manual.
So did my old e30 325e.
My Scirocco on the other hand uses 5008 bulbs in the running tail lamps,
which are 10 watts.    This is what is stipulated in the DIN book and
approved by the German Tuv.
I can understand that you want bright tail lights however and I objectively
looked at my Vanagon after dark last night.
Its true that the lights are small , but mine are not dim.
I cant make a comparison with a Schwinn bicycle as I've never seen a Schwinn
with lights on it, but my own bike has a german generator set on it and the
bulb is .06 watts in the tail lamp .

I am not blowing smoke as I have documentation.

I am concerned about lights being overly bright and there being a poor
distinction between running lights and brake lights.
If your BMW has the same wattage bulbs for the tail lights as for the brake
lights then it is wrongly set up.
Sincerely,   Steve Cotsford