So, not a super bright projector, but every mode is capable of over 800 lumens. In a theater style room that's plenty for even large screens such as my old 128" Stewart Firehawk. In my current theater the BenQ W1200 effortlessly fills my 124" wide 2.35:1 screen - Studiotek 130. From a practical standpoint that's the equivalent of a 131" 16:9 screen, from a brightness standpoint.
The important thing is going to be your room. If you have side ambient light, look for a screen that's high contrast and gray, for rejecting a lot of side ambient light. My Firehawk was like that, as are many screens including the Da-lite HC Da-Mat, Elite HC Gray... I had great luck in my not overly dark great room at muy last house with projectors not quite as bright as the W1200 projector, on a 128" screen. (my walls were a medium rust color and ceiling and floors where light (but not white).
If your room has ambient light but not from the sides, those HC gray's aren't going to help that much, so you might be better off with a nice "plus gain" screen - say 1.3 to 1.6, to brighten the image. That won't help though if your ambient light is back where the projector is.
Whatever your room for the BenQ W1200, I offer the same advice - should you be able to pull it off. Darken the walls, ceiling and floor of your room. If you can't do it all, do what you can. But, if you can do nothing else, and can manage to darken the wall your screen is on, that alone will make a real difference. If you have the usual off white ceilings, darken them several shades - They will likely still seem as bright to everyone, since the ceiling will likely still be the brightest surface. That worked in my old great room. I darkened the ceiling several shades, and the result - well less than half the reflected light getting back to the screen. - And no one noticed the ceiling change.
To make the point, I'm still getting used to my new theater. With its black ceiling and dark blue walls and floor, just about any projector now seems bright. The W1200 caught me off guard. I might of guessed that it was breaking 2000 lumens, until Mike "enlightened me" with measurements not much more than half of that. My room works very well!
Screen size - the whiter the surroundings, the more lumens, or smaller screen to look good. Still, even in a light walled family room this home theater projector can do a respectable job on a 100" diagonal screen, with some ambient light, for sports viewing. In my testing room with the side walls turned to light surfaces, it filled my Carada Brilliant White 1.4 gain screen rather effortlessly. It's a 110" diagonal 2.35:1, so it's only about only about 90" diagonal with a 16:9 HD image.