Projection Screens 101?

[KapHn8d]

My brain hurts.

So, I was pretty set on the Sony VPL-VW285ES (perhaps considering the sister 385 with the automatic iris for the contrast enhancement) until I started poking around with some different calculators. I have mas-o-menos 21 feet of throw in the roughly 15'x24' room and without making a mess of where the projector can be mounted or leveraging screen gain, the otherwise-incredibly-sexy Sony 4K offerings under $10k are suggested to be not quite bright enough.

I see the new JVC offerings are pretty stellar performers in contrast and brightness in exchange for eShift5 up-sampling versus Sony's native 4K/UHD.

Can someone point me to a reasonable resource to learn about screen material differences and gain selection? Stewart seems to be at the epicenter of this technology with an incredible reputation and history, but when I attempt to decipher their fixed home cinema screen material options, I end up with more questions than I brought to the site.

This would be fixed frame, wall mounted, non-retractable, probably not auto-masking ($)... is Cima FF (Neve) what I should be looking at?

Any advice here would be sincerely appreciated...
/c