I don’t really think handedness plays any part in this honestly. I use my implants in both hands just as easily. However, if there’s specific readers you’re trying to use, that would effect things. (Ex: if there’s a reader you have to interact with from your car to get into a parking garage, you might want that chip in your left hand. If there’s a reader on the far left side of a door, it might be easier to scan your right hand.)
If you want the absolute easiest reads, I would recommend positions 1-3. I tend to have an easier time with getting reads in the wild from my implants in positions 1 and 2 then the ones in position 0, but those locations are certainly not as beginner friendly. I’d assume that the blade of your hand would also be fairly easy to get reads from then in P0, but I don’t have an rfid chip in mine to verify.
The reason I recommended against putting the xM1 in the blade of your hand is really just for potential futureproofing. If you don’t think you’ll want another xG3, then there’s no harm in putting the xM1 there. None of this is permanent though. You can always move/remove the xM1 later if you so choose, so don’t worry about it too much!
There’s absolutely nothing wrong with the positions you’re looking at, I’m just giving my thoughts. Feel free to take them or leave them.