I use a 'Round Rectangle Tool' to create navigation bar (for website)..
How to remove two rounded corners at the bottom?
Once it has been removed then I can apply some style from blending options.
I might use either Layer mask directly in the layer or group the layer(s) and put layer mask into that group instead.
Option 1. Layer mask in the layer.
altkey while you click the Layer mask icon at the bottom of layer panel.
This way Layer styles will adapt the visible shape of the object.
Option 2. Layer Mask in a group.
Do exactly the same thing as in Option 1. except select group when you click Layer mask icon.
Putting Layer mask into a group will allow Layer styles to retain the initial area of the object.
This has some advantages at times. For example if you don't want shadow to start curving inwards right where the objects bottom starts or if you don't want to retain that bevel at the bottom.. etc..