I've also been using 801's nearly since I started vaping with an NPro ~ got tired of refilling!!
I used penstyle for ages, until the Janty Stick came out. The regular or manual 801 batteries are ridiculously expensive, that's why I went to the stick. Battery is about $4 vs $12-18. Longer lasting charge as well.
So far I've mostly just used the fluval that comes with the carts, tried other things but always just go back....if you have fluval to cut you need to experiment a bit ~ cutting the fluff the same size with a little "proud" to hold it in works best, it can't be too tight and won't let loose of the juice, or too light and won't hold it enough and leaks. It does get soft and gunky after a week or so, so replace often...washing occasional (I just rinse them and blot with paper toweling...they're pretty re-usable, but watch for thin-thick places ~ throw those out.) They're so inexpensive to buy empties.
Some use a straw inserted beside the fluval, I use a needle bottle for refilling. I really think air flow/juice flow is better with a straw ~ I use part of a plastic q-tip shank, about the right size. They're kinda hard to find anymore. Some use part of a coffee straw (some have two chambers, you can divide them.)
You also need to 'trim" the white casing of the cart (a 1/16th - 1/8th inch) so it doesn't quite touch the bridge in the atty ~ they will scorch, and that's awful tasting! Just make sure to keep the fluval a tiny bit past the edge of the cart after trimming to keep contact with the bridge. Better juice flow.
I love 801's. And the whistle tips are a must!
You made a good choice, but like everything else it takes a little bit of practice to get optimum vapor.