The television show "Outlander" is largely set in the Scottish Highlands, in and around a laird's castle, in 1743. A few linguistic questions:
As depicted in the show, the principal working language of the castle's noble residents and common employees and hangers-on is English, but certain ceremonial actions are conducted in Scottish Gaelic, which is still universally understood. Private conversations among townspeople seem to generally be in English. Is this an accurate portrayal of language use?
A clergyman attempts to conduct an exorcism (in Latin), and the congregants participate in prayers in Latin? Wouldn't the Highlands have been Presbyterian at that time, and what language would religious services have been conducted in?
Catholicism was still prevalent in some areas of the Highlands, and I've heard sermons could be in both Gaelic and Latin depending on the priest and the congregation. The Hebrides were known for their Gaelic sermons, which many took over seas to America. Yes, a lot of Scotland was Presbyterian, including the Highlands but there still remained some pockets of Catholicism and even Episcopalian.
Remember, this is TV even if the author/director (what have you) read a lot on the subject they're trying to sell a product. I'd imagine a fully Gaelic tv show would not sell well, even though that'd be quite accurate. Lairds would mostly be bilingual and so would other educated Scottish Gaels, but many of the lower class would be monolingual.
Some books to read on this:
Highlander: The History of the Legendary Highland Soldier by Tim Newark
We're Indians Sure Enough: The Legacy of the Scottish Highlanders in the United States by Michael Newton
White People, Indians, and Highlanders by Collin Calloway
The last two are focused on Scots in America but their are numerous chapters on the conditions and culture of Scotland during the 1700s including religion and language.
/u/lngwstksgk is another great source of info on this topic.