Yes. It will play any 4K UHD Blu-ray, standard HD Blu-ray, or DVD-Video with unparalleled video quality. It will bitstream all audio and video formats—including all four HDR formats—that are currently available on those discs. It will natively decode all Dolby and DTS formats, including the lossless and immersive ones. It will also play back multichannel uncompressed PCM correctly, including 4.0. It can feed any decoded audio to its internal DACs and output up to 7.1 channels over unbalanced RCA (plus, it has dedicated stereo outputs, including balanced XLR—just like the Oppo 105 and 205).
As for the sound quality of the DACs, I couldn't say, but I have read that they are quite good. They had better be at that price point. I elected to go with the step-down $600 DP-UB820-K, since I'm using audio over HDMI to my receiver, and I couldn't be happier with the video quality. It definitely beats my Oppo 103D in that regard. The UB900 has a few extra video processing features, mainly for projectors, so it could look even better (depending on your display setup). It would undoubtedly sound better than the UB820 (and probably also the 103, albeit with the caveats previously mentioned re: formats).