No apologies, that’s what this forum is for!
Yes.
The thumbnails and preview images are JPEGs that live in your PhotoStructure library. See https://photostructure.com/faq/library/#where-are-my-librarys-database-settings-and-preview-files
Rendering is all done at import time to make browsing fast.
V0.9.1 uses dcraw, which supports many raw formats.
v1.0 (which I hope to have alpha releases ready in a week or two) switched to libraw, which supports many more recent raw formats. The only raw format that I’m aware of that it doesn’t support yet is cr3, which they say will be ready soon.
Currently, yes, but thinking about it more, it seems like it would be better to import it if possible: most raw images have fairly large embedded JPEG images that I can use for full-screen. I’ll think about this some more: thanks for bringing this to my attention!