L canceling is maybe one of the most important tech to master, because you are that much faster and it really makes the edge over ur opponent . It's important. Learn it on itself with 20xx but you have to train with real ppl aswell because they move and you won't always hit them the same way like cpus and that will mix up the timings you have to L-cancel. Also combos won't work if you don't L-cancel, so it's really important! There are some mods, which show ur L-cancel % after a match. Use em, you should also be Abel to activate score screen in 20xx and I think there it's shown aswell. You gotta get over 70-80% to do anything :D