HDMI connectivity is a great choice, as most computer have built-in HDMI outputs. USB connectivity adds the convenience of presenting without a computer
XGA (1024 X 768) with 4:3 apect ratio or WXGA (1280 X 800) wide-screen resolution provide crisp, clean projection.
Brightness needs vary, based on the size of the room and whether it can be completely darkened. An average size room with lights that can turn off requires 1,500-2,000 lumens. A larger lecture hall with a large screen and moderate light requires 5,000 or more lumens. A movie theater could require over 20,000 lumens.
Long Throw projectors are for large rooms and large images. Short Throw projectors are designed to be positioned 3 to 8 feet away from the screen. Ultra-Short Throw projectors are designed to be positioned 4 feet or less from the screen