Sorry for going dark for a bit - I flew back to the US from Ireland yesterday and spent a while offline.
EDIT: Also forgot to ask this but I assume that the G400s or something with the original design will always be kept in the product line for those loyal followers or am I wrong?
With regard to the link, I'm not sure what you would want me to comment on except that there is no CPI doubling in the Proteus Core. Every CPI step is native on that sensor.
The sensor did not have the ability to have more granular steps at the time. With Hyperion Fury, 80 CPI steps have been made available.
Just like with the G400 or G400s, non-native steps for G602 in automatic game detection mode are calculated based on data from the next-higher step. So 600 is calculated down from 750, 800 is calculated down from 1000, etc. Hyperion Fury only has native values with 80 CPI steps.
The power consumption of the G400s sensor is significantly higher than the G602 sensor. It would have a battery life that is lower than G700s.
Beyond report rate, endurance mode also changes other internal tracking parameters of the sensor. The net result is less good performance than we can call "gaming". This is different from the G700/G700s because those sensors have far fewer variables that can be adjusted for power savings.
They are very different products with very different components.
G400s is being replaced by Hyperion Fury.
Depends on your hand size, really. The lip on the top right side next to the RMB is about 5mm wide, so you can conceivably go 2.5 fingers up if you don't want to go 3 up with your middle finger on the wheel button. G400s has about 10mm of space there, so it will feel different. It's also rubber rather than plastic with soft touch paint that the G400s has. Hyperion Fury does remove the severe lip on the right side that totally prohibits some people from using it with two fingers on the side, though.
Much like with G400s and G500s, there are features in Proteus Core that some people dislike, while other people like them greatly. If you want a reasonably weighty mouse with hyperfast scrolling and weight/surface tuning, and that is worth an additional $20 to you, then Proteus Core may be the mouse for you. If you prefer a lighter mouse with fewer features, Hyperion Fury could be a good choice.
With the specific criteria you listed, I don't know that Proteus Core would be worth the additional money. I can't really make a strong recommendation either way with limited information, though.
Glad you like the changes. As far as the weight goes - it is ~5g lighter than G400s, so not a huge amount of difference.