The Flow has a top cap that unscrews to fill, smooth threading and only one full turn to remove, with two massive cutouts to put eliquid in (I can actually fill it readily from the big 8ounce bottle I mix my adv in).
The Wotofo .25 ohm coil is nice, very little break in, quite good flavor and vapor at 37w. Actual resistance of the one I'm using is 0.34 ohms.
I haven't used a smok tfv8 head, so can't compare. DJLsb just put out a review of the Flow yesterday; the whistle he notes only happens if the airflow is barely open, nudge it just slightly more and no more whistle.
Since I like to build my own coils, but being able to use readily available prebuilt heads is nice just in case, this is a good tank for me.
The Flow actually holds 5ml, likewise a positive. When I get the rba in, drop back to 23w, time between refills will be solid.
On the Oceanus, it comes with two 20700 batteries in the box, a nice touch. Not sure if they include an 18650 sleeve. 101vape has the base mod (w/batteries) for $45. I'm waiting on 3fvape - their price will be the same, but include an ISub V E tank (the tank will be another pif item, since I prefer my own tanks)