Hi Jan, welcome to the forum!
- can i create tours with pop up images and videos visible in oculus go?
yes, overlay images and videos are supported
- is it possible to make transitions between two panos with same view (day / night effect)?
Transitions (fading etc.) aren't supported yet, but you can use a hotspot to switch between different panoramas.
- pano2vr is the editor for all these features, right?
Yes, VR Tourviewer focusses on supporting Pano2VR tours, only very basic krPano tours are supported.
Note that skins, maps, animation and menus aren't supported yet.