The answer is, "it depends". And it comes down to which coil you are using. The single coil RBA works ok at lower wattages but there is almost no flavor for me, multiple coils require more power. I use the quad coils in the pair of TFV4's that I have and run them at a minimum of 75 watts and usually between 80 and 120 depending on
juice. 75 produces a cool vape. Anything below that is pointless for them. You might want to look into a different tank for that mod. Subtank minis I have are great between 35 and 40 watts with the .5 coils. I am not even sure the mod you have will fire the .15 coils in the TFV4.