Soul Eater

[Buffalobiian]

Are only technicians able to see them, and not the weapons?

I don't think so, since both technicians and weapons need the skill to tune their souls together to create something like a Witch Hunter. I believe seeing other's soul is an extension off that skill. As Stein said before, he can see other's wavelength and tune his to theirs to neutralise their attack.

Even if he could see them, would he really look for information he could get out of them or even care at all?

If it's bigger than his he would.