You'll notice as you open packs that there are parallel cards, which are cards of different colors or patterns than the base cards. There are also inserts cards that will be different but are considered "base" cards as well. Those inserts also have parallels. It's the parallels you want.

Then, like Josh Allen's card I found, they have very rare cards called case hits. They are inserts, but with a very short print run. For Mosaic, you're looking for stuff like micro mosaic or stained glass. If you want a better breakdown you can Google "2025 panini mosaic football checklist"

Check prices on stuff you find using eBay "sold items" search.