I will try to answer your questions as you have presented them.
First, the 1.3 gain Cinema Vision material is usually the best choice for a CRT projector. This material does the best job at reproducing colors and has just a little bit of gain to help the CRT projector.
As for the frame, here are a few comments on each.
This screen is a 1-1/2" square tube frame system and the fabric is snapped to the back and then hung to the wall.
This frame is a 1 5/8" rounded front extrusion and the fabric adheres to the back of the inner frame section via Velcro.
Clearly the best of the three, this frame is a 3" wide 1-1/2" thick frame that has a beveled (angled) edge that extends back towards the screen surface which is attached to the back via snaps. This helps to eliminate shadows.
Which ever frame you choose, please give some consideration to purchasing the frame with our "Pro-Trim" finish. This is a velvet-like finish which helps absorb light around the screen to create a "black-hole" type of affect around the screen. The cost to add this is minimal and it is well worth the money spent.
Hope this helps.