I started out with a lot of blue/brown coloured PET (I don't trust PE with overly aggressive flavors (shortly mentioned in the vid as well)) dropper bottles for mixing and storage. They're easy to (re)fill, but the tips on the >50ml bottles are too big for some liquid fill holes on atomisers, in particular the fill holes in the top gasket of my TFV8 BBB, so I had to fill liquid from my 60ml bottles into the smaller 30ml bottles just to then have something to fill my BBB with. Stupid :ß
So while I still use those bottles for experimental mixes, I also got myself a handful of 120ml Gorilla-type bottles (with really small tips) for juice storage and for everyday filling purposes, plus 2 tall but thin 30ml Gorillas which fit nicely into the sleeves in my portable ecig case. They're not as comfy to refill as the regular PET dropper bottles, but since I don't re/fill them as often, I don't particularly mind.
One thing I learned over time: While PET bottles are rather hard to squeeze when they're new, they do have a mild weak spot in their walls, probably due to the production process, which you can feel with your fingers, and if you keep on pressing that spot when using the bottles, it becomes pretty soft and very easy to squeeze after a while. That was shortly mentioned in the video, too.
Concerning bottles with topcap pipettes:
I considered buying bottles with topcap-integrated pipettes, but even if you're lucky enough to find bottles with pipette tips that are not bulky/round (and therefor largely unsuitable for refilling atomisers), you're still left with the problem that the integrated pipettes are never long enough to reach the bottom of the bottle; just like it was mentioned in the video. What a useless product.