Are there any consequences for cancelling a credit card within a year/the fee waived period?

Usually the banks impose a 6 months min period else they can crawl back any points/perks that was issued to you.

I don’t believe cancelling a card affects your credit score

Not paying your bills on time would affect the credit score

Had a card that had in the T&C that they would clawback the welcome gift if I terminated within six months - so check with your issuer if any conditions there.

But if you wait until annual fee charged then terminate because you are unwilling to pay (or the bank is unwilling to waive lol) then you should be fine.

For credit score side - early termination doesn't hurt score (in fact may help as they consider total available credit as a (negative) factor and terminating would reduce the negative effect of this factor. Do note however, if you are planning to churn (terminate with intention of applying for new card), one negative factor is applying for cards too often.
If you are very concerned on credit score - every time you get a new credit card (or are declined) you have right to get free copy of your credit file. It is quite informative about your score and what positive/negative factors affecting final result.