How to create multiple panoramas (or HDR photos) from multiple groups of photos at once

you may have a look at the batch features of https://ptgui.com (rule based batch builder for creating multiple stitching projects from arbitrary file/folder structures and batch stitcher for rendering panoramas from these projects).

I think that for Photoshop's Photomerge, the best one can hope for is the semi-automation of some very basic steps, which will still involve manual steps for the processes that can't be automated. It's not a one-click or batch process by any stretch.

As for batch HDR automation, I have a faux-HDR process using stacked files, smart objects and mean stack blending mode, which can be fully automated by feeding in a folder of say 30 images and the script would then batch stack and blend in groups of images, i.e. 5 at a time. It would then automatically create 6 separate "HDR" toned images.