personally always download the "complete disc", so I get all the special features, soundtracks & subs etc.
the most convenient way to play the downloaded "complete disc" movies (BD, 3D, UHD 4k etc,), you'll need to invest in a proper multimedia player, there are many options out there now in 2018, I use something like the Zidoo X9S. These multimedia players treat the downloaded files like a disc, for most titles they can even load the disc menu, so you get pretty much the full disc playback experience, and HDR, Atmos etc all work the player can passthrough them to your AVR.
just copy/move the "complete disc" files onto a portable HDD or flash drive, plug it into the Zidoo X9S's usb3.0 port, and play, simple as that, no need the hassle/time to convert files or burn discs.