I thought I'd add some information that I was struggling to find after a lot of unsuccessful searching but ended up having to figure it out myself.
I have a 2019 M550i G30, I picked up a blackvue DR900S-2CH and a Power Magic Pro as well as the fuse harness kit from the dashcam store.
I've determined that if you want park mode, you CANNOT wire to the front passenger fuse box, it has no BATT+ (yellow cable) supply that stays on, the entire fuse box shuts off after 5 minutes... You can only use this box if you don't want park mode.
I thought the rear fuse box was going to be a big pain, but it wasn't difficult at all, actually it's easier than front box since there's more room and you don't have to be upside-down and contorted to work on the box. I used F273 for my ACC+ which turns off after 5 minutes. I used F230 for my always-on BATT+ line. There's also a ground point right there that takes 10mm socket. I found it easiest to completely remove the screw, then strip the ground wire for 2 inches, wrap it around the screw, then put it back together and tighten. there's also a great spot in the right to stick the magic power box, I then bundled everything up, used electrical tape to keep it together, as well as tape the cigarette adapter to the magic pro end so there's no chance of it slipping out (it's not super-tight on it's own). there's plenty of room to put this wire bundle to the left and below the fuse box and I was back together in short-time.
I ran power along passenger side and the rear camera cable on drivers side - took all of 20 minutes to cleanly route both, the included tool was perfect. there's lots of room for one cable, but 2 cables is a bit much on the same side.
So the short of it - If you want park mode, save yourself an hour of screwing around with the front box or searching the web - it doesn't work. just go straight to the rear fuse panel.
One other thing - I expected the Power Magic pro's light to turn on at some point while I was wiring things up, it DOES NOT!. I wasted a lot of time and thought my box was bad. you figure with electric going to the box, it should light up right? NOPE! it only lights up after everything is connected and then you turn the car on for the first time... there must be something in the box that kills it until it gets power on both BATT+ & ACC+ and then from there on out the LED works fine all the time.
A second thought - the rear fuse panel has a paper card folded up there showing all your fuses.. if you need a new one of those go to
https://www.bmw.com/fusecard to download the one specifically for your car. just plug your VIN in
Final thought - the fuse panel has no spare empty fuse spots. you'll see what appears to be empty slots, but if you look closer you can't actually put a fuse there since it's missing the underlying fuse receptacle on the board. you must use a piggyback fuse (or whatever they are called)