I may be skewed by the fact its the plug of my country; but i like the type L plug (its the no 1 in the photo) mostly because its modular: you dont need to get a specific faceplate to have a certain arrangement of plugs, switches etc... You just take the brace plate off and you can rearrange the fruits in the box to your hearts content. Eg: you pass an ethernet cable and need to put a keystone in the wall; you just buy the fruit and put it in the place of a blanking plate. What i dont like is the almost total lack of shielding for the live and neutral.

The smallest is the best. I don't know which one is the smallest, but I want that one.

L5-20 and L6-30

Honestly USB-C. It is getting added to electrical outlets. Super small, basically impossible to get electrocuted being low voltage DC.

Works in every country.