You’re not lazy for asking, especially since I’ve never found clear directions for macOS users. It turns out to be simpler than I expected and I’ve been meaning to post the directions:
Step 1: Remuxing
Use tsMuxeR to “mux” (multiplex) a Blu-Ray friendly MKV into a Blu-ray compatible ISO:
The official Despecialized MKVs are already Blu-Ray friendly. Add the MKV file in tsMuxeR, and use the checkboxes to remove any audio tracks you don’t want. You can also add subtitles here too. (I find this part of the interface very annoying. I prefer using MKVToolNix first to create a custom MKV with the audio and subtitles tracks I want, then remux it with tsMuxeR, but it’s totally optional.)
In the lower half of the window under Output, select “Blu-Ray ISO”, give it a Disk Label, a file name and saving location.
You don’t have to touch any of the other settings, just click the “Start muxing” button. It should only take a few minutes to create a Blu-Ray compatible ISO.
Step 2: Burning
I’m on 10.13 High Sierra, so the follow instructions might be slightly different with previous versions of macOS:
In the Finder, select the ISO file, click on the File menu, next “Burn Disk Image….” A new window with pop up with a few options, which I leave alone. I do make sure that it’s at the lowest burn speed since faster speeds can risk errors that will make the disc unusable. Click “Burn.” With my burner at 2x it takes about 40 minutes to burn and 20 minutes to verify.
I’ve read people recommend special burning software (ex. Toast) but macOS can burn Blu-Ray ISOs just fine, as long as the ISO is Blu-Ray compatible. I think the advantage of Toast is it can create Blu-Ray ISOs from MKV files with menus and such. If you’re not looking for anything fancy, tsMuxeR and macOS’s built-in burning capabilities is all you need and they don’t cost a dime.
I don’t know what a nzb file is about and I haven’t had to deal with them.
I hope this is helpful.