In terms of lenses, DOF adapter, etc. What size or specs should I look at when buying lenses and things like that? Hopefully that's not a confusing question.

The Canon HF has a lens thread 37mm in diameter for attachments.

I just bought the the Canon Wide Converter and it works very good, little distortion/barreling, and I'm happy. It provides a field-of-view of around 30mm (35mm equivalent), and I think still not very wide. However the build quality is very good.

And with a wider lens, that means even wider depth-of-field, and less opportunities for selective focus, isolation of a subject, etc.

What I hate about all camcorders is that the sensors are so small that even it F1.8 isolation of the subject is often impossible, with few exceptions.

I have a Kodak Retinar 37mm WA adapter and it is totally blurry on the HF100. Even at full wide only the center portion is more or less sharp. Works pretty well on the Elura 100 though. So I might have to get a Canon adapter, or maybe Raynox.