Just do what you think looks good…
These young bucks telling you what to do, largest wheel they ever pushed was on a Huffy vehicle… Don’t mind them. :lol
19s are waaay overkill on an E36 in my opinion. Anything larger than 17" on an E36 looks awkward to me. But on an E46 like yours, 19s don’t look bad.
If you end up needing the fenders rolled by the way, you’ll probably pay $25-$40 per corner that needs to be done.
You can also buy a tool to do it yourself for $260 (below):
http://www.tirerack.com/accessories/detail.jsp?partnum=LIPROLLER2&make=Tire+Rack&ID=52
Or you can do it ghetto style for pretty much free:
Good luck.