First, I will say that this issue only seems to manifest on my Dell Optiplex 740, a machine which some might consider to be ancient by today's standards. I don't seem to have this problem on my much newer and more high-powered Dell Lattitude laptops which I use for work-related tasks.
The machine that I'm dealing with is running Windows 10 Pro, build 1909. Using NVDA 2020.1 with Microsoft 365 Home. Using Espeak but I have access to Codefactory's Nuance/Eloquence synthesizer as well as Acapela.
In a Word document responsiveness is noticeably sluggish when I navigate through a document, particularly when navigating character by character with left/right arrow keys. Here are some steps I can take which slightly improves responsiveness.
1. Restoring the document from a maximized size.
2. Setting the document to draft mode from the view tab.
3. Enabling UIA support in Advanced Settings.
While these three steps do help the fact is that responsiveness is still slower than it is with other programs, such as with Wordpad or LibreOffice Writer. At one point the problem seemed to have gone away but it is now back. Also, sometimes characters are occasionally not spoken when I navigate to them and increasing the caret timeout seems to make little or no difference. I'm open to any suggestions which may improve NVDA's performance with Word.
Blindness Assistive Technology Specialist
JAWS Certified, 2019