Re: COMRIE parish or MUTHILL?
Someone wrote: "Muthill is a small place, smaller than Comrie and much smaller than Crieff I would be very surprised if these other places had ever come under Muthill for any administrative purpose." That is absolutely correct.
However as we are talking about the late 19th century, there is no point whatsoever in considering the relative sizes of villages and towns in the 21st century. You have to get into the habit of thinking by parish. The parish was the basic administrative unit.
The map from FamilySearch is not at all helpful in this context. It shows Ardoch as a separate parish, but in the 1790s, when the (Old) Statistical Account was written, and in the 1840s when the New Statistical Account was written, it was part of the parish of Muthill. Look at the map at https://stataccscot.edina.ac.uk/static/statacc/dist/county/Perth (noting the absence of Ardoch from the list of parishes) and read the accounts at https://stataccscot.edina.ac.uk/static/statacc/dist/parish/Perth/Muthill
See also https://www.ardochparishchurch.org/ which explains that the parish of Ardoch was not disjoined from the parish of Muthill until 1857, though there was a Chapel of Ease there in the 1780s.
(Chapels of Ease were built in parishes where a significant number of people lived in the parish but many miles from the parish kirk. In this case, about five or six miles, which would have been a weary trek there and back on foot to attend Sunday services, especially in winter.)