Night and day difference for me between 1.14 and 1.14.1-pre1. A lot better. After logging in, take about 2 minutes for all chunks to render. I can fly without hitting any unrendered chunk when surrounded by land. In 1.14, I could run into an unrendered chunk. Oceans still seem to have an issue. I can easily row into an unrendered chunk when by an ocean.
Issue appeared immediately with previous releases including 1.14.4-pre-x
I cannot reproduce this issue in 1.14.4. Server has been up 2 weeks with 2 users playing a few hours a day.