Maybe the OP's "not that important" was an unfortunate way to put it.
I think the answers you ask for are in Ordinatio Sacerdotalis[0]
[0] https://www.vatican.va/content/john-paul-ii/en/apost_letters...
That's the infallibility of the extraordinary magisterium. The Catholic Church also teaches that the Pope possesses the infallibility of the "ordinary and universal magisterium", which makes less than ex cathedra statements infallible, when he teaches something and (almost) all Catholic bishops agree with the teaching.
But, I think many Catholic theologians would say, that whatever infallible teaching Francis gave by the ordinary magisterium, was largely just a repetition of what his recent predecessors had taught, without any significant doctrinal developments. (Probably the biggest point of contention is the status of his catechism change on the death penalty, but I think even the majority of theologians who support the change wouldn't argue it was infallible.)
An example of a teaching which many Catholic theologians say is infallible ordinary magisterium is John Paul II's 1994 declaration that women can't be ordained as priests (Ordinatio Sacerdotalis) [0] – which wasn't teaching anything new per se, but arguably the first time it had been stated with such explicitness and solemnity
An interesting meta issue, is that theologians debate which papal statements are infallible, but the judgement of a statement as infallible isn't itself infallible. So, while Cardinal Ratzinger (future Pope Benedict XVI) issued an official declaration in 1995 stating it was infallible ordinary and universal magisterium, [1] that declaration itself isn't infallible – and some (progressive-leaning) Catholic theologians have argued the declaration is mistaken. [2] Conversely, a minority of (conservative-leaning) Catholic theologians go beyond Ratzinger and argue Ordinatio Sacerdotalis is infallible extraordinary magisterium (ex cathedra). [3] Some even argue the Pope can teach infallibly and then erroneously claim he wasn't doing so. [4]
[0] https://www.vatican.va/content/john-paul-ii/en/apost_letters...
[1] https://www.vatican.va/roman_curia/congregations/cfaith/docu...
[2] https://womenpriests.org/teaching-authority/mag-con2-theolog...
[3] https://www.catholicculture.org/culture/library/view.cfm?rec...
[4] https://canonlawblog.wordpress.com/2015/11/24/i-agree-with-d...
Ordinatio sacerdotalis, 22 May 1994, Pope John Paull II
https://w2.vatican.va/content/john-paul-ii/en/apost_letters/...
