I believe GK will be changing all new 14m Sonics with 63cm bars and the valves will have stopper balls too.
The 63cm bar makes it night and day on the 14. So that's definitely the bar that needs to be used on the 14. However, I don't think GK should put stopper balls in the bladders, I don't really see any functional need for it, when you pinch the valve, there is no air loss, at all. When you have a ball and the air is still leaking, you can't pinch anymore due to the ball, need to cope with, so I don't like them, as I don't need them. Actually I don't care, ... whatever...
My two cents on the 14 is that it pulls a lot, and there is no reason you would want it any bigger. Usually after a session on the 14, my legs are wrecked, and I feel physically exhausted having dealt with that much power. It's quite pleasant though, but I need to go back to cross training! Upwind and jumping on a standard board at a medium 10kts with more than 85kg, that's the bottom end. Can get medium 8kts with a door-like board, and get all the mates pissed off to see you jumping when they need to keep an eye on their kite when they walk upwind or submarine. Note that the 14 is very stable, and stays effortless in the air unless the wind drops to something ridiculously low. Time to pack then.
Basically I'd say it develops the power of a much larger kite, and with side by side riding with others, that would be something like the power of a 18.
You can depower it as much as you want pratically, but when you're asking for power (and sure you do), you get that much power delivered to you, be prepared for that
So Lift is there for sure, plenty of hangtime, stuck in the air high and for a long time, and it is reasonably fast turning when you consider how powerful it is. Fast enough for various kiteloops, but nowhere as fast as a 12.
So overall I think it's a really good big kite, but you'd need to be heavy or really looking for a lightwind machine, don't be fooled by the "14" printed on the kite, in your usual reference system, think more like a 18.
Usually I like to ride a smaller (max 12) faster kite that can be moved all over the place, trying to get more power from my kite, more efficiency with my lightwind board and position to achieve my lightwind goals, instead of having the power of two trucks available and tapping into the depower most of the time. That's really personal preferences, and in this personal context, the 14 feels almost too big for me and would only fill the 9-11kts gap. Since I'm somewhat busy (not always too busy since I write shit on this forum...
) and I can get some stronger wind every now and then, it is not indispensable in my quiver. If I was somewhere when it is consistent light, it would be a major part of my kit.
Anyway, as usual, try it yourself!