Hi Artur,
So with a little searching we know that the iStick will go to .5Ω no problem. Eleaf recommends the Melo clearo for that (Wonder Why??LOL) mod. I have never used a Melo but I have seen one. They look nice but I personally am enjoying the Subtank mini from Kanger. the thing that kept me from jumping into an Atlantis, or the Melo was the lack of RBA mainly. Secondly I was not keen on the ceramic wick material used in the Atlantis or the cosmetics of their tank, but they do get mostly positive reviews from many folks.
Keep in mind that I have been building coils for a few years now so that was a deal breaker for me personally.
But having said that I have used the stock coil(my wife has been using them consistently for ~6weeks) and I can say without a doubt they are great, and capable of producing great vapor at 30w, and beyond..... The Subtank mini has good airflow full open(better than the Lemo IMO) two tighter settings and can be run all the way up to about 50 watts and still wick well with thinner liquids. If you Vape thicker liquid you can expect your max to be around 35ish without having issues with wicking. With that said if you are content with stock coils I would personally prefer the Subtank mini, or the Melo mostly due to their cotton coils and secondly due to their cosmetics.
Basically Chalk up a Vote for the Subtank from me.. Good Luck, Happy Vaping.