How to indent every paragraph, excluding headings?

Questions
2

This doesn’t answer your question of will you regret using the native styling, but if you want “fully” indented paragraphs see if something like this works for you:

#show par: it => [
  #set align(right)
  #let indent-amt = 1em
  #block(width: 100% - indent-amt)[
    #set align(left)
    #it
  ]
]

Some styling rules might not work as they did before because you are now inside a block instead of a par, but it does e.g. indent after tables