My first PV was "The Fifty One" Duo. It reminds me of a KR808, and I've read that you can fit the cartos on a KR808-A. (I belive my adapter is a KR808-d). I absolutely LOVED the Coffee,...then I bought a package of their Chocolate,... Been searching for that flavor ever since. (reminded me of unsweetened chocolate baking powder).
I took it back because I didn't like the battery life. First battery would die before the second one was charged leaving me haning for 10-15 min with no vape.
Then I got my 510, and I love it. Three days after getting it I quit smoking analogs, (thats when I finished the pack I had, and never bought another one.)
Since then I've picked up a 510-901 adapter and a 510-801 adapter, and their respective atty. I instantly understood the posts I read about the 801 and throat hit, and the 901 and flavor.
I won a package of KR808-d cartos in a contest here on ECF and liked them, but not as much as my others.
Along with that I picked up a bunch of Loranns flavors before I knew what I was doing. I ended up with Lemon, Orange, Anise, and Clove that are oil based and not usefull for vaping. I got a great deal on a gal of 99.7% pure VG, and found that I can get PG for arround $5 for 4oz at a compounding pharamacy two blocks from my house.
If I had it all to do over, I'd go right to the 901, then get an adapter to go to 510. (I'd skip the 801 till later) I'd get the PG/VG and order 60ml of 100mg unflavored, a DIY kit from DIY Flavor Shack (my next order), and the RIGHT flavorings.
All in all, I'd probably be just about where I am, with the only real change is waiting on the 801, and the differences between the 510 batt and the 901 bat.