A great viewer is not a culling workflow
FastStone opens almost anything, fast, and costs nothing for personal use. If you mainly need to browse, view, and do light edits, it is hard to beat on price. We are not going to pretend otherwise.
Culling is a different job. You load a card, race through a few thousand frames, rate the shots you'll use, reject the rest, and move on. Our app (called PhotoTaken) is built around that one loop: RAW and JPEG show as a single tile and rename together, card ingest copies to two drives and verifies the copy before you trust it, and your ratings and color labels are written to standard XMP. Because the picks travel in XMP, they show up in Lightroom, Capture One, or Bridge when you open the same files. FastStone keeps its tags in its own database, so those picks stay put and do not follow the photos into your editor.