I'm more concerned that anything that isn't matte will show the unevenness in the wall that you talk about and make it stand out. I've had this argument with DH and the architect over the years and I've folded and gone with matte for the very reasons they state....no lap marks, reduces the impact of imperfections in the walls.... The only way I know to avoid lap marks is to paint it once and paint it well...it's when you go back over stuff to catch those areas where it's thin or didn't cover completely that you really see the sheen build up and it shows. I don't see a pic of the room.

I was wondering if I should paint my ceiling beams the same color of my walls. Will have two tone walls, Light on top and darker on bottom with white chair rail.

You could treat everything at or above the opening as the "ceiling," and everything below it as the "wall." My mom has told me that they would do this in old houses to make the room seem bigger, or something. Otherwise, yes, paint it all the same color. There were lots of cove ceilings in my 1930s neighborhood, and most people painted the ceiling and walls the same, or had a picture rail to paint up to, e.g.: But I think an actual picture rail might look odd in your room. I had a coved ceiling without a picture rail, but the ceiling was odd and gave me a stopping place: You could get a similar effect with just paint.

Here is my space:6/12 pitch and 14 foot 8 ceiling without structural ridge! My problem is this, the scissor trusses designed by engineer appear to be too massive in the mock up by my contractor? They obviously begin at top of my 8 foot 6” wall. The 6 by 12 Douglas fir beams he specified are 23 inches lower at the sides( lowest part of truss). My contractor will do something different and possibly a cross beam is simpler. Any suggestions. The beams at 1/3 the angle would be closer to 11 feet