I guess I’ll ask. How much mountain bike riding have you done?
Usually wish lists come from experience. If you have ridden 3x’s, 26ers, rim brakes then you would have a foundation. Frame geometry plays a part.
Typically someone gets a bike, preferably used, and then does a few mods along the way so they know what they want in their next bike.
Having built a few mountain bikes, $400 unfortunately won’t get you there, even without your list.
John