As far as demeanor, the INFP is a bit more animated than I might be normally (maybe she's in an ENFP mode as she is "performing"), but I can relate to her in some ways. I gesture a lot. I pause mid sentence to gather my thoughts, to sort of convert them into something others can (hopefully) grasp. Most INFJs I've known have a warmer vibe, not unlike the INFJ here, but less reserved. I am usually more or as reserved as INFJs, but when I am "warm", it is more intense, and their warmness seems more even. I realize this makes INFPs seem "inconsistent" to people - we seem "hot" or "cold". Of course, INFJs can have nasty tempers also, but I'm talking about everyday demeanor, not emotional moments.
Their views aren't necessarily how I see myself/INFPs or INFJs, but I don't disagree with their basic concepts. For instance, I am very guarded/private, but I am open to people/ideas in the sense that I withhold judgment on others until I feel I have enough info. My demeanor is not inviting, nor do I share a lot of personal feelings easily. Info/facts are not that hard for me to put out there though.
Whereas, INFJs may seem to judge quickly which seems "closed", however, their demeanor can seem warmer to me in its Fe politeness, which reads as "open" to me. They seem to express their feelings easier, but withhold personal information. So they toss out beliefs on external global issues, expressing judgments easily, but they won't discuss their personal life. I think both types guard deep emotions, but maybe INFPs discuss shallower ones more if it's a tool to relate to someone (to get the OTHER person to open up). This may add to the open effect, but it's deceiving to those who think that is the extent of the INFP's emotions & feelings, or to think we are expressing them for their own sake.
I don't think it boils down to "open" vs "guarded", but maybe open & guarded in different ways.