Can you explain more about how Lutz requires a moving axis? [...] and does it work similarly for a Flip (since I presume the only difference between the two is the take-off edge)?
[...] In that case, would this mean Boyang is the best among the three in terms of axis control (not sure how to call it)? Because I understand that both his 4Lz and 3A are good, how does it work for him?
I tried to demonstrate Yuzu's axis problem with the Lutz here:
https://mobile.twitter.com/Henni147/status/989866483479203840
As you can see in the pictures, Nathan has a very clean left outside edge and he leans his full body to the left as well (naturally along the edge).
Yuzu enforces a left outside edge by twisting his ankle and leaning his body in the opposite direction - the same axis position as in the landing (a right back outside edge with natural leaning to the right). He's also twisting his hips and rising his left shoulder to create momemtum. That can't work, we remember his fall at NHK...
Another problem with Yuzu's Lutz take-off is that he's not using his right toe pick but the full blade to assist the take-off. That's technically wrong and should be counted as an (awkward) 4Lo by the technical panel. Nathan is only using his toe pick. Boyang dito.
The funny thing is: in his record freeskate in Barcelona Yuzu used the same correct take-off technique as Nathan and Boyang. This strange ankle twist comes and goes in Yuzu's Lutz attempts for whatever reason. I don't know why.
The flip jump has a nearly vertical take-off edge, so the flip requires a slight axis movement as well (not as much as the Lutz though). Yuzu could fix this problem quite well, since his current 3F looks very solid to me. His success rate on the flip over the last three years is remarkable.
Yuzu's 4T is decent as well, but sometimes he tends to slight underrotation in his landings, especially in the 4T+3T combo. His 4S might be less successful, but when it works, it's the best quad in the men's field.
Boyang has a brilliant jump technique and great control over his axis. Technically I would say, he's currently the best jumper in the world. In the overall quality including entrances/exits, soft landings and other features Yuzu is still unbeaten imo.
#Sidenote: I'm not a competitive skater and I wouldn't call myself an expert either. These are just my perceptions after watching countless jump slomos and animations from different angles
