If you will allow me, I think I might be able to answer some of your questions.
The Cinema Vision fabric with your NEC 9PG+ is a perfect combination. In fact, I have the Runco 900A (same as the NEC 9PG +) with a Cinema Vision screen in my theater. It is the right combination considering the lack of brightness from the CRT projector. It looks great. As for the comment about sparkly issues, that is not longer a concern. As the projectors began to be brighter there was a need to reformulate the screen and since that time (about two years ago) there are no sparkle issues. Also, the Cinema Vision fabric is ISF approved.
Now, lets talk about frames. In your post you mentioned the Da-Snap and the Imager. Let me explain how each is designed and perhaps that will answer your question. The Da-Snap is a 1-1/2" square frame and the fabric is attached to that back of the frame with snaps. The frame is then mounted to the wall with brackets that hold it just slightly off the wall so that the snaps do not touch. When you look at it from the from the front the frame hides all of the mounting and provides a black border around the surface in a "shadow box" type of look. From very close up on the sides you can see the snaps but you have to be very close.
The Imager screen is much different. The 2" aluminum extrusion used on the Imager is designed with an inner area which allows the fabric to be attached via velcro very close to the front of the frame. However, it is attached inside of the frame which means that the frame hides the attachment point to make it a clean look. This allows the fabric to be closer to the front edge. The frame is then mounted to the wall with brackets that are hidden when the screen is put in place.
Yet another type of fixed wall screen to consider is the Cinema Contour. Considered by most to be the "high-end" fixed installation screen, the Cinema Contour is a 3" frame with the outermost 1-1/2" flat and the innermost 1-1/2" angled back towards the fabric. This helps to eliminate any shadowing that can occur when ambient light hits the screen. With the Cinema Contour the fabric is attached with snaps but they are hidden behind the frame and a small lip on the outside edge. The mounting brackets are very similar to the Imager and when the Cinema Contour is installed all you see is the frame and the fabric. It provides a clean installation and is very simple to assemble.
Regardless of which of the three you choose, give some consideration to adding the Pro-Trim option to your choice. The Pro-Trim option provides a black velvet-like finish to the frame which helps to create a "black-hole" like affect around the screen to absorb any light spill around the image. There is a small fee associated with this option but it is well worth it. Even if you choose not to go this way, the frames are all provided with a matte black powder coated finish.
I hope this helps in making your decision. If you need more information, please let me know or call our sales partners at 800-622-3737. They are very knowledgeable about these products and can answer most questions.
Blake Brubaker, CTS
Vice President of Sales
Da-Lite Screen Company, Inc.