From what I see on telly, the little Waleses are lovely and v. normal. They are excellently behaved at public events and show just the right amount of personality at those. They seem to know each other well, enjoy each other's company as much as siblings can and care about each other. Since Louis is the youngest, it's natural that his older siblings would boss him a bit and that he might be comparatively more wiggly.
As for screen time: not much
If the pupils at my prep school are any indication (and my school plays matches against theirs) not much and most of that is supervised/directed.
Ours come into school for 8:15-ish and stay until at least 4:15pm, some until 6pm for activities (e.g. swimming, tennis, board games, mythology, history, bird watching). They occasionally use screens in lessons for learning reasons: e.g. White Rose, Dr. Frost or times tables rock stars for maths, Linguascope for French, Atom for reasoning.
The school supplies the device and it is controlled and monitored by the school and set up with stringent restrictions. If a pupil tries to look at anything out of bounds, a message goes to IT who contacts the head of year or similar.
Many pupils, especially in years 6, 7, 8 have their own phones or pads or similar but they are not allowed to carry them in school and if they do bring them in (so they can call home if they are boarding) must hand them into Matrons' for safe keeping. At boarding, after dinner, they play informal sport (football, cricket, dodgeball, table tennis or similar) , watch films, make biscuits, read or draw.