Can BP handle a high traffic website?

Hi all. I have some questions for you techy people out there. I’m researching the website I want to build this year. It will be a community website similar to a dating website where people can search for people by location and by criteria. I need chat areas and other bits and bobs that BP cater for. But as I plan to do media for the subject, I’m expecting high jumps in traffic and hopefully a good high traffic website in general. I now know I will need to move my hosting from Hostgator to somewhere like WP Engine for this. These are my questions:

Can the BP software itself handle high traffic?

If I have say, 20 BP plugins – will they slow my site down even with caching?

I know the benefits of having a site built from the ground up means I can have more functionality (but for now I think BP has everything I will need), so apart from the functionality, what are the benefits of getting someone to build a custom site for me – also what price range will I be looking at for that?

Many thanks,

Kris