Hi,
To answer your questions, Front sights are generally sized to work with the factory barrel mounted sight. When we install an aperture sight on top of the receiver it generally raises the rear sight level which can often (not always but generally) require a taller front sight.
You can fold down the Browning sight and look over the top just fine.
Aperture sights work GREAT for those of us with aging eyes. Scopes (everyone has their likes and dislikes, its what makes life FUN and entertaining, and I do not care for a scope on my lever guns. )
Hope that helps!
ANDY