The boost you get from countering a two or three drop and jumping to five or six on your next turn is a much greater swing than countering a four drop and then having 8+ mana for the main reason that you don't have that much useful to spend that kind of mana on very often and if you do it is not as significant as an earlier mana boost
It also pairs well with the underplayed Faeburrow Elder, offering another path to infinite mana with Gauntlets of Light
NEOs channel lands are great, with Takenuma, Abandoned Mire providing recursion and self-mill while Eiganjo, Seat of the Empire pads the interaction section
The early game plan is simple but effective: get Fynn onto the battlefield, start attacking with cheap Deathtouch Creatures, and try to put at least one Poison Counter on each opponent as quickly as possible
During this phase, any abilities or spells that trigger take place
An excellent blocker if you need one to most likely definitely put a chill on attackers, but it gets better