Duotone recommends the 22m lines since the kite is a 12m. Generally kites 12m+ will benefit from slightly longer lines, but what really counts is your personal preference. Duotone does offer a 19m line-set. Put that on a M/L Trust bar or M Click bar and you'll get the FASTEST turning (stock) set-up!
Going with 19m lines will translate to mostly a loss in power, but an increase in turning reaction. I think Duotone sums it up pretty well...
19 M - 70% HANDLING / 30% POWER
Fast and reactive turning
For extreme Freestyle, Wakestyle and waves
Tight, super fast and hard kite loops
22 M - 60% HANDLING / 40% POWER
Fast kite loops
Favourite set up of our Freestyle riders
Best choice for wavering
I've personally not noticed a change in the performance or drifting properties when going with shorter lines on the Neo. Only a change in the handling which to me is the faster turning/reaction. I mostly use the 22m lines, but I've noticed the power change when going up/down from 24m lines. I think 19m lines would be pushing it for me, but I'm a bit curious to try them out.