Its normal for boas to stretch out and stand up when out. They want to explore. Mine do it a lot if i'm doing stuff with them on me. It's worse outside. They will try and grab anything I walk by like rain gutters and branches. Also on my deck in the summer time, my big girl will sometimes try and grab the gutter to the roof lol.

As for hissing on the table, it might have just been her breathing. Some larger boas can get vocal when out and about or excited. it's just them breathing. It sounds like air escaping from a hose lol. You will know when a big boa hisses at you or so I've been told as none of my girls have ever hissed at me but my big girl does breath heavy sometimes when shes out and about and determined to get places I don't want her to get lol.

Temps and stuff are fine. She stops and watches you and tenses up when you pick her up means she doesn't trust you yet. Give it time.

She sounds like a normal acting boa to me. Mine do pretty much the same thing except the stop and tense up part but I've also had them for years so they are used to me and the house so they just go about their business even if someone walks by them. most of the time, if someone walks by, they will actually try and check it out or just ignore it lol.