This stopped working like this a long time ago; if you put something in quotes, Google will still sometimes return pages that don't include it, or that contain "synonyms" for it. You need to turn on the verbatim option for the old behaviour, I think.

Verbatim has worked for many years.

both verbatim and the quotes don't act the same as the + operator did

This is something else that used to work - but for the past few years it only seems to make it more likely that the search term is in the page. Very annoying :/

"like" "so", or "like so"? Because the latter means that it should be present on the page, as well as in that order. I'm not sure about the former though.

The former forces both "like" and "so" to be present in the result without any further relation between them. It's awkward and unintuitive, but it was specifically introduced when they remapped +.