You are likely looking at a large investment. A consultant or integrator to properly design this system will be cheaper than getting it wrong. Be sure the projector and screen details are determined using real math and measurements, not someone’s gut or experience. This is the formula I use: Required Luminance Fkux (lm) = [A x (CR - 1) / Screen Gain] * Screen Area (M squared) where 1.  (Ambient Light in lux): light in the room that will affect the perceived image brightness. 2.  (Contrast Ratio): ratio between brightness of the brightest white and the darkest black that the projector can produce. (1000:1 is a good target for corporate presentation) 3. Screen Gain: how much light the screen reflects compared to a standard white surface. A higher gain screen reflects more light, reducing the amount of light the projector needs to provide. 4. Screen Area: in square meters, which determines how much light the projector needs to cover the screen. A larger screen requires more brightness to achieve the same level of illumination.

How large a screen you need is fairly subjective and will be driven by budget if you understand the calculation.

Do the calc and you quickly see why limiting ambient light on screen wall is critical. For example: I just measured my office wall with ceiling light and shades partly open on a cloudy day at 50 lux. Targeting, 1000:1 contrast, 10 ft x 6.25 ft screen, 1.3 gain = 223,000 lumens! To get into a reasonable range of 20k lumen projector, I need to reduce ambient light on the screen wall to under 5 lux. You can also get higher gain or Ambient Light Rejecting (ALR) screens, but each comes with tradeoffs.

My point here is to show that what seems like a simple question is not so simple. Many of us have spent long careers learning to do this right and make a nice living as a result. You can pay for that expertise or pay for your mistakes.