Juul has invested an astounding amount of research, time and money into their products, to a level that none of the other vape manufacturers has ever achieved.
For diminutive it may looks, the Juul is a blend of the best available technologies.
Because of the extremely accurate and reliable TC design, of the uber-efficiency of the electronics and the alchemically complex formulation of their e-liquids, your attempts to find something comparable to the Juul are mired to failure from the start.
I refill the Juul pods regularly, I dry the dew-absorber every time, and they last 6 - 7 refills; but the taste of refills cannot compare to the original.
There are aftermarket refillable Juul pods, but they aren't good as the original, as there is a lot of hidden technology in them which isn't replicated.
I use the Smok Fit (a differently shaped Infinix) when the Juuls are flat, they compare as a caveman torch to a laser, but I get my nic.
In general, I use the pod systems for social vaping, preferring the Therion and Dani boxes with Kayfuns/SS316 and Kabukis whenever/wherever possible.
My suggestion for optimal vaping, is to use a number of different devices, for the different situations which develops during the day. The Juul is the perfect pod, almost irreplaceable in its class, but other moments and situations of the day may call for a different class of devices, as you will see fit.
Best Regards,