Re: Which are the essential buddypress theme pages needed to edit?
If you are starting fresh with a BP child theme, all you need to do is look at the files in bp-default to decide if you need to customize them or not. I know that sounds sort of open ended but with the way child themes work, some time you might need to copy and edit every file but other times you may need to only touch one or two.
My approach has been to create the initial child theme style.css file and then start with the “regular” files – home.php, sidebar.php, index.php, archive.php, etc. just like a normal WP theme. I only copy a file from bp-default into the child theme if I really really need to modify it. Most of the time you can easily add stuff via actions and filters in your functions.php file. The advantage is this can be much more portable if you redesign your site in the future – just copy functions.php into a new child theme and go from there.
Really it’s best to just systematically go through bp-default and decide if you need to tweak each .php file or not. In most cases, you probably don’t have to. 
