Thank you for your reply, and for letting us know.
You have been so patient, and obliging!
Next thing to check may be the trackpad settings.
With some settings the trackpad may be pausing to make sure you have finished tapping / clicking..
To Check Trackpad Settings"
Click on the black "Apple" on the left in the top menu bar.
Click on "System Preferences" in the drop-down menu that opens.
Click on "Trackpad"
Choose "Scroll and Zoom" on the top menu of the window that opens.
If "Smart Zoom" is ticked, click the tick to untick

Now you won't be able to double-tap to Zoom,
however, the reading performance may be slightly improved for you.
There's another setting too:
Again: System Preferences
This time: Accessibility
Then: Mouse and Trackpad
Next: Pointer control (left menu)
Next: Trackpad Options (at the bottom)
Uncheck the "Enable dragging" option

Hopefully changing the settings may help improve on the delay you've been experiencing.