So I was thinking of finding a connection to an angel group, but as it turns out one of the funded companies in there portfolio is a similar (but not direct) competitor. The platform / idea is close, but it's a different niche. Should that discourage me from submitting to them and attempting to meet with them?
Assuming that the two companies can be considered competitors -- which in the VC mind would not just be application -- but potential applications and potential application of the underlying technology, then:
I would not put it on the top of your list. Unless they have a history of funding multiple companies in the same space I think you might be best focusing elsewhere. You don't have to avoid them -- but focus your time on the most fertile ground.
There is another strategy as well: Who would that angle group see a "competitor"? Maybe you will be able to say:
So where do you find a "competing" funder? This is a purely psychological thing. Ask people in the industry. Look at who funds the competitors to companies in their portfolio. Are many of the principles BC folks? Well, then find a fund whose principals are mostly BU. Perhaps a former principal at the Angel Fund when and started their own gig? Perhaps they are big donors of a specific political persuasion, and their opponents are across the street?