Withtout being able to see into the panel I would approve the installation.
The one staple to the left does seem to be streched and could be replaced by a few with only two wires per staple.
Door bell xformer at panel O.K. I've seen some people try putting them inside the panel. [Linked Image]
When mounting the panel on a basement cement wall without a backboard, an airspace to prevent corrosion would be recommended. In the old days, as a helper, my job was to paint the plywood used for backboards flat grey. Haven't seen any painted boards in years.
NM at the bottom of the panel might need support or protection. Can't tell.
Don't understand anyone considering the NMs above the panel as being bundled.
Wire staples or plastic saddles the Code just requires them to hold the wires in place.
Good job.
Alan-- (Inspector)

Alan--
If it was easy, anyone could do it.