Totally agree about the load rating and as what @karlos said. Tyres ain’t what they used to be. My wife’s T-Roc is heavier fully laiden Vs the bus.Yeah. Use a phone or Sat nav if you require perfect speed reading.
My spare is a compromise that will ‘get me home’ it clears on the front and will cope on the back , it’s in the spirit of a space saver.
The load rating and pressure thing has been done to death. Modern low profile tyres are designed for vehicles way heavier than our buses but that do 100mph and can corner too.
I work in a risk environment. The incidence rate of reported cases of tyre failures due to being of an unoriginal size? Zero, IME. Low risk.