I agree this would be very difficult to answer because everyone likes something different.
As far as mods go and ease of use....
I really like each one I have.
iStick TC100 - dual 18650, light weight, easy battery swap.
Cuboid - dual 18650, heavy, but easy battery change.
RX200 - triple 18650, heavy, battery cover isn't quite as easy to remove but last longer due to 3 batts.
IPV3 Li - dual 18650, light weight, sliding type door but just works. (squared corners so not quite as nice in the hand)
I run from 53 watts to 78 watts depending on what tank I have on.
For those that I use temp mode, I am still trying to dial in my choice settings so nothing to report yet.
- The Herakles (original) using the .6 coil is the best flavor producing tank I own for my particular flavor. It is bottom fill only and holds 3ml juice so maybe not as easy as you'd like. Maybe it'd be different with other flavors but I only use one flavor in it so I can't compare.
- The TFV4 is top fill, my second best flavor producer(using the quad coil), and holds 5ml juice (although burns through it quickly)
- The Crown is top fill, holds 4ml juice, and just works.
- I'm still trying to decide exactly where the Herakles PLUS fits in here but it is top fill and holds between 3.5 - 4ml juice depending on if you fill from top or bottom.
- The Steam Engine is top fill and holds 6ml juice plus has juice control.
Each of them are great in their own way and offer something a little different.
If any of this helps, great.
If this just muddies the water, sorry.