I had posted the same annoying problem several months ago. It seems like real-time typing cannot be achieved when the file is relatively big. From then on I broke down a file into many smaller sections and it started to work without delay. My suggestion to Evernote is to announce the file size that works on real time. I have had this delay problem for a long time and it is a shame. Nevertheless I am still using Evernote since I have to access my files from several devices.
Thanks for the same comment to Evernote and I wish Evernote can help our problems.