On the face of it, I have to question the relevance and/or probity of your questions: at least the one to me.
Simply stated, I’m pointing to what I call the Pat Robertson fallacy.
If Pat Robertson announces God told him something, the only way you can logically claim God DIDN’T speak to Pat Robertson is to for God to tell YOU he didn’t speak to Pat Robertson. So unless you are willing to claim God spoke to YOU, you can NOT logically claim he didn’t speak to Pat Robertson.
I think both the questions are completely relevant. If mm was claiming assuredly infallibility, then she could be charged with making herself a pope, but if she was expressing a belief (based on evidence) in the Bible as being inerrant, then she herself in not claiming such, but only presenting a judgement based upon evidence, being dependent upon a greater authority than herself to persuade people by manifestation of the truth. (2Cor. 4:2)
And which appeal to a greater authority is what you yourself do in asserting that Rome is the One True Church, based upon Scripture, Tradition and history, rather than the Orthodox or others who also appeal to their church as effectively being the supreme authority on doctrine.
This assertion of Rome as being the OTC flows from your fallible faith decision to submit to her, and which fallible human reasoning you must exercise on discerning which of many pronouncements and parts thereof are infallible (and thus require implicit assent of faith), as well as (to varying degrees) the meaning of these and those from the Ordinary magisterium, which most of what RCS believe and practice is said to belong to. And in which there are many differences beyond a unity in core essentials.
Thus neither adherents of SS and SE (sola ecclesia) believe they are assuredly infallible, but appeal to greater authorities which claim to be, and under both models there is division, the differences being in degrees, as well as a wide unity in core essentials.
The question then remains, are you saying that no one can have Scriptural certitude of truth (and thus believe and speak the same) except by confidence in the magisterium of Rome when it speaks infallibly?