In AU/NZ think the default limit is like $75–$150, depending on the type of shop? With Apple/Google/etc Pay in AU/NZ, the same limit seems to apply as with chips.

Above the limit, with Apple/etc Pay, I usually need to sign and have the card physically on you if the merchant asks for it. I think even my Paywave card requires a signature if used via Google Pay, but a Pin without, but I almost never use that one for large transactions.

Above the limit with Paywave/Chip/etc would make you enter your pin (and you already have the card on you).

If you're paying for expensive things, Apple/Google/etc Pay is a bit worse UX in my experience.

Your comment is unclear, and I can't tell if you're talking about any of the above happening in Australia or elsewhere.

In Australia signatures are not considered a valid form of identification for transactions.

It's PIN or nothing.

That's actually not true either. It depends on the card and the issuer. In particular, contactless Amex cards will occasionally fall back to signature.