Is the Optoma HD39HDR a true 4K projector?

No. It has a native 1080p DLP chip and accepts 4K HDR10 input, downscaling it to 1080p. The picture is sharp 1080p, not native 4K.

Is it good for gaming?

Yes. Enhanced gaming mode gives an 8.4ms response time at 120Hz, which suits fast console and PC games. Turn the mode on in the menu for the lowest lag.

How bright is it, and can I use it with lights on?

It outputs 4,000 lumens, enough for lights-on viewing on a large screen. Bright mode shortens lamp life, so Eco mode is quieter and lasts longer.

Does it have built-in streaming apps or Wi-Fi?

No. It has no smart platform or Wi-Fi built in. You add a streaming stick over HDMI, and wireless screen mirroring needs the optional Optoma WHD200 adapter.

What screen size and placement does it support?

It projects 30.8 to 301.4 inches diagonally with a 1.12-1.47:1 throw ratio and 1.3x zoom. It is not short throw, so it needs several feet of distance for a large image.