along the way I have tried all(most) of the mods and fillers. Here's my 2 cents:
The blue foam is my absolute favorite. since switching over to the blue foam a couple months ago--it has significantly reduced my dripping and/or topping off the cart. the 510 cart holds about 12 drops, push the blue foam into the liquid, fluff back to the top of the cart. The blue foam is smaller than the other fillers and basically acts as a plug. has also reduced leakage and cheap.
https://strictlyejuice.com/index.php?main_page=product_info&cPath=67_49&products_id=222&zenid=jtgvb089bhg01lveia595l0kk7
My second choice is fluval 2 plus found on amazon or at petshops. its an aquarium filter that is easily cut to size for carts of all sizes. fluval makes many types of filter material, but the 2 plus works the best over all.
Pyramid tea bags were too much work for me and never seemed to wick as well. polly fill and such were either too fibrous or would give off a burn taste.
Ultimately it comes down to personal preference.
Happy vaping