I want to add that westminster PM’s cannot in normal circumstances issue anything like an executive order. Everything has to go thru two houses and a lot of public scrutiny before stuff actually happens - ie as normal legislation. To this end I would opinion there are less stupid surprises. The PM is three things; an administrative power within their own party, a figurehead to the public voters for said party, and a foreign ambassador to just about everybody else. The rest of their job is being another minister at the fancy shouting table.
Eh? There is administrative law in parliamentary systems, just as there is in presidential ones.
Sort of. The built-in majority in the House of Commons makes major decrees that have no parliamentary angle rare and unnecessary; they can issue Statutory Instruments or Orders in/of Council and they usually get the blessing or tolerance of Parliament anyway. Parliament is intimately involved in them.
If we had a separation of powers like the US, however, plus the current degree of partisanship, I’d imagine their scope and detachment from Parliament to increase.