I'm a little confused. The abbreviation "cartos" typically is used for cartomizers (integrated cartridge and atomizer) rather than cartridges. The Kr8 (sometimes abbreviated 808) uses cartomizers. The DSE801 penstyle does not. It uses separate cartridges (carts) and atomizers (attys). Sorry if I sound pedantic, but I want to make sure we're clear.
DSE801 cartridges certainly should come with polyfill in them. [I am not referring to the empty mouthpiece, which comes with an atomizer (that does not have filling material), but to the separate cartridges (usually in a box of five).] Ask your supplier about it.
You can fill them with PTB (or the blue foam mentioned in your signature). Or you can remove the white cartridge, just use the mouthpiece, and drip (on the atomizer). Your preference.
Personally, I think carts are a pain. I only drip. But that's just my preference.
