I don't know that there is a "best" pen style vape, and some of them are really unforgiving of drops, as you have found. You can pick up some vape bands in almost any vape shop for a pittance, that may help with drops.
If you are serious about ecigs, you may want to invest in a more robust setup that gives you more vaping options. If you are "wedded" to the pen style of vaping I don't have much to offer, as I don't use them. It will be a matter of preference.
If you want to "move up" a bit in vaping, the pico kit is fairly well liked. You can get it with an internal battery and a more MTL vape (it comes with the Melo II I think). The newer pico comes with a Melo III, which is a bit more powerful and would give you more vaping production (possibly more than you'd want, hard to say for sure). The other kit I often recommend to newcomers is the Aspire zelos kit, which comes with an internal battery but it's a bit more robust in terms of power, before needing to recharge (can get a 50 or 75 watt kit, and it comes with a well liked, easy to manage Nautilus 2 which is definitely a more "mouth to lung," restricted tank, probably more similar to a pen style of vaping.
Both aren't as slim in form factor, but they are still pretty small, and in my opinion anyway far more robust.
Best of luck with whatever you decide.
Anna