Optoma HD27HDR is a 1080p projector if I remember correctly. In that case, you may need to upgrade to a 4K projector to enjoy the 4K contents in their proper form. At their current state, you chain them up like this to consume the 4K contents from the media player if supported. Additionally, you can get a Firestick 4K; these days, streaming platforms have tons of 4K materials.
WDTV Live Medial Player > HDMI > Denon x2100w AVR > HDMI ARC (Not sure if your projector supports) > Optoma HD27HDR projector
edit:- improvise