On a "Sweet Sixteen" photo, you want everything to put attention on the subject. You should be able to choose where the photo is taken, so you should start off with a location having nothing in the background, or anywhere else, that would take attention away from the subject; you don't have to make everything else bland - it just needs to complement the subject. There is no reason to 'fix' an issue in PP when that issue can be prevented when you take the photo.

Do we know with certainty that the EF-M mount is not useable with FF sensors?

Pentax is the one manufacturer that is openly tepid to MILC; their identity is wrapped up in the pentaprism, and they're having enough trouble releasing new FF lenses people say they need.

I don't do video. For stills, I use gimp ... I find it to be just as useful as PhotoShop, and I don't have a reason to complain each month.

But no EVF - harder to use without tripod, virtually impossible to use in sunlight.

The problem with one lens solutions is that they force too many compromises on the designers.

With the possible exception of the first one, all of the images feel too tight to me. I would feel more comfortable if you had left more space around the building in the first place .... but, of course, that is not something you can "fix" at this point.

I used to have automatic updates disabled on my Win 8 machine, which is why it was still a Win 8 machine and not a Win 10 machine ... and then it died. I definitely didn't want to purchase a new Windows machine, which would have forced me into Win 10, so our daughter put together a new machine mostly using parts from various donor machines {including memory from our old machine}, and now I am typing this on an Ubuntu Linux machine.

DPReview has published a series of pictures from a tour of the factory where Nikon makes their own glass.

https://www.dpreview.com/articles/3583146192/inside-nikon-hikari-glass-factory

Nikon has already said they'll be using Z-mount, but right now all we know about it is the name. Canon has already introduced the EF-M mount for cameras such as the M-1 and M-50, but as I indicated above, I don't personally know whether it can handle FF or whether they'll find themselves supporting four mounts at some point.

Incidentally, I was at BestBuy this morning recycling a printer, so I stopped by their camera department. I was very much impressed by the M-50. If I were still a Canon user, I would consider it for my next upgrade if the price would come down a tad. I'm expecting the M-series to completely replace the 'Rebels' in a fairly short period of time.

From my perspective, the main advantages of MILC are EVF and CDAF .... both require that light hit the sensor 'at all times', so they require being in LiveView mode.

Canon already has the EF-M mount and an adapter that enables all existing EF mount lenses to be fully used. I'm not sure of the specs, though, in particular whether it would accommodate FF.

OP used the words 'First Communion'; those words usually go with 'worship service', which conventionally goes with the words 'no flash'.

Shouldn't NR processing be applied to images in the buffer?? I would expect that to slow the camera down only when the buffer is full.

Yes, there is very little you can learn from theory here. Take lenses out into 'the field', see what each does through the viewfinder, take some pictures, and 'study' the results back home. Experience is the best source of understanding.

The thing missed by most participants in this discussion is that subject motion is just as bad as camera motion - and Image Stabilization does nothing to 'fix' subject motion.