In my opinion, if you are looking for a refillable pod system device, then look among the series of some major brands.
Voopoo (Argus or Vmate series) - my wife has a Vmate.. it reproduces flavors very well.. the liquid is easy to fill and the liquid level is easily detectable.
Geekvape (Wenax)
Vaporesso (Vibe) - my wife’s next pod is already at home in the closet, two devices, a pallet of coils.. everyone who uses it praises its flavor reproduction and it has a decent liquid capacity.
Lost Vape (Ursa) - my wife’s other pod.. in my opinion, its flavor reproduction is a notch better than Voopoo’s, but it has a smaller liquid capacity.. refilling is more difficult (at least you have to get used to it) and the liquid level is not easily detectable, at least not on the Ursa Nano Pro, but she really likes it.
Innokin
Aspire (they have good ones too)
It is important that you can buy coils for the given device later, preferably from many sources.