Hi, great questions! I did, however, have to delete the images you posted here, as they did not seem to be yours. Because of copyright issues, we do not permit people to post images that are not theirs. You can, however, link off to them. That said, you might want to add a link to Bubolinka's photos in your original question above.
As for your questions . . . briefly, molds and mats do different things. Typically, you pack modeling chocolate, fondant or gumpaste into molds and pop out the edible material later to create a piece with lots of dimension and depth. Impression mats and textured rolling pins are generally for adding textures to sheets of the above materials; with mats, you press or roll the fondant on the mat so it picks up texture. With rolling pins, you roll the pin over the pre-rolled fondant sheet to add texture. (So mats and textured pins are just two different tools for doing similar things.) Gumpaste cutters are just that - cutters for cutting shapes out of rolled fondant, gumpaste or modeling chocolate. It looks like Bubolinka probably textured her heart pieces with either texture mats or rolling pins, and then cut out the heart shapes with cookie or gumpaste cutters.
There are countless sources for these tools online (if you Google this stuff, I bet loads will come up). One of my favorite sources of molds is First Impressions. Food-grade rubber stamps are very hard to find. Sweet Stampen claims to be the only food-grade source of rubber stamps, but her selection is very limited. I use craft stamps that I sanitize before use.
Hope this info helps a bit.