Hi Imeo, Esterigon looks really nice- I really like side button mods and yours looks very interesting. I didn't understand Todd's review either- I think he maybe has a preconceived idea that side buttons are innately inferior as they have more contact surfaces, but I disagree with that idea as with a bottom button, you don't have a really solid connection between the button and the tube as it must slide easily and not jam, so most of the current must go through the spring which must be a problem with magnets that so many use nowadays!
I can't see a reason that your design shouldn't have the lowest resistance of any ss mod providing all the contact surfaces are clean and you have certainly made that easy to achieve! I would probably buy one right now if it weren't that I only had my current setup for a few months and my atty is 23mm so would look a bit weird! I quite like the look of the Erlkoenigen though and it's 21mm so I may treat myself in the next few months. Or wait for your new atty ;-)
The voltage drop test video you showed isn't really showing the voltage drop of the mod- it's a combination of mod and battery drop. The actual mod drop would be much less. Any chance of doing a test which eliminates the battery from the equation like Atmizoo did on their mods here:
Voltage Drop Tests: Roller, Dingo, Guppy | atmizoo vaping modware ? That would certainly show how low it is and I don't see a reason for it not to be lower than the best bottom button mods out there.