Shower niche in load bearing wall
I'm in the process of designing my shower and would like to have a wide ~30" shower niche. However, the wall that the niche is going into may be load bearing (running perpendicular and down the center of the overhead attic trusses). I want to go ahead and frame out the shower niche as if the wall is load bearing.
In addition, I'd also like to install some recessed medicine cabinets across the bathroom in a 2x6 wall that may or may not be load bearing. I believe it's 2x6 to fit the 3" vent stack for the toilet.
Can someone point me to tables/charts stating what size header I will need for the different scenarios? I'd be removing one stud for the niche and one for the medicine cabinet and the walls are second story interior walls beneath an attic.