Will this screen be appropriate to be used at the conference of 100 people? Does the screen look cheap?

You can definitely use this piece of equipment. When the screen is set up it looks good and most people are delighted by the quality, but it depends on seating arrangements.
The screen does not look cheap. The material is like a heavy gauge canvas. The poles are aluminum and the right size. It’s fairly easy to set up. There is no sound from blowing fans like the blow up screens. The next step up would be using the wall. You’ll be amazed by the magnitude of this screen, should work fine for indoor use or outdoor presentations held later in the evening.

For more information please check out our guide setting up a great backyard setup
http://outdoormoviehq.com/ultimate-guide-to-outdoor-movies
Or take a look at our recommended projectors and screens
http://outdoormoviehq.com/outdoor-movie-screens