Regarding the 07:xx Glasgow - Inverness, I am unsure if the additional calls at Lenzie and Croy were to cover for a withdrawn Glasgow - Stirling/Alloa train during the pandemic or not. Between Larbert and Dunblane, the Glasgow - Inverness is behind the Edinburgh - Dunblane.
In 1998 to round about 2003/04, the Glasgow - Aberdeen (which ran every 2 hours) used to call at Lenzie and Larbert between Glasgow and Stirling on Sundays Only, as the Glasgow - Stirling/Dunblane local did not run. There was initially "No Sunday Service" at Bishopbriggs or Croy, but in recent years post Turbostar, the Edinburgh trains called at Croy on Sundays, and the Glasgow - Stirling/Alloa started to run on Sundays which meant Bishopbriggs had a Sunday service, with the Lenzie and Larbert calls in the Sunday Aberdeen trains being removed.
For a good number of years until the second half of the 1990s, the Edinburgh - Glasgow via Falkirk was switched to run via Grahamston instead of High on Sundays. This provided connections into a Grahamston - Dunblane shuttle. The Edinburgh - Glasgow was revised to run via High on Sundays as per Monday - Saturday, with the ex Dunblane extending to Edinburgh.
The Inverness trains have remained broadly similar throughout, mainly due to the various single track sections meaning that the timings or frequency cannot be radically altered unless there is a double digit layover at each of the passing loops.