Congrats on the M7. Lovely choice.
I was thinking about the photo you posted, Johan. Isolated subject in focus. Distracting background downplayed through the use of wide aperture DOF. And the problems of making such photos: erratic subject movement in a narrow focus plane; changing light and shadow.
Well, this is the realm of the sportsshooter. It's what they do for a living. With very specific tools: fast auto cameras and fast telephoto lenses.
Pared down to the non-professional, one choice would have been an SLR with predictive autofocus and aperture-priority autoexposure mated to a medium focal length, fast telephoto. E.g. Canon A2 + 135/2 lens. Cost = USD $800 used. Your choice of 400 B&W to go. Those kids will be frozen crisply in motion with the backgrounds hauntingly blurred away. Just like any good sports photo.
I make this comment not to discourage buying a partially auto M body. Goodness, no. But it struck me while reading the various posts that an RF, no matter which body, isn't really close to being the right tool for what you described as your goal.