Not sure if this is mentioned. But previously I had made the graphical changes mentioned here in developer options to help with lag. Also did the svoice button fix. Lag was better, bit typing, especially with SwiftKey was laggy, driving me nuts. After a lot of experimenting I found the standard, default accuweather clock/weather app (beautiful widget btw) was the culprit. I removed it and boom. Night and day. I can again type at full speed with SwiftKey as I did on my note 2. Lag is completely gone. I found this by fiddling with limiting processes (to 4) in development options. I noticed this widget had to constantly restart.... So removed it and returned running process option back to default. Try it. Like a new phone.