They could vary from manufacturer to manufacturer slightly. So may not have a 'standard'.

I happen to love shaker style, but it kind of depends on the mood/style you're going for in the rest of the house. Your floating shelves are already a bit modern/transitional, and most of what you see from the back of the island is glass upper cabinets so I think you could easily go the modern/transitional direction with the clean doors. If you're more into traditional, and are planning on going that direction with light fixtures and furniture, etc., continue with the shaker.

Magdoline, another option is to have all benchtops white or light coloured, the island and full-wall cabinetry in a dark material, and all your other cabinets white/light coloured (Incl those in B’s pantry). OR all joinery in B‘s pantry in same dark material as island and full-wall cabinetry. A mixture of light & dark joinery can be very striking.

There are indeed building code safety requirements that govern the design of balustrades, including the gaps around panels. Sometimes compliant gaps at the maximum opening look a bit off. I find that smaller gaps, 20 - 50 mm often look more pleasing. You say your patio is not covered. In that case there is little potential for any balustrade to trap heat. An uncovered north facing tiled patio will be a heat sink, and a glass (or substantially open) balustrade will allow more sunlight onto the tiles which will increase heat gain. A solid balustrade may reduce that heat gain due to it's shading potential, but I am guessing you want glass for the view, so if heat is a problem, consider adding a roof covering to shade the patio.