I work primarily on histories of photography as well as intersections between art and literature in the 19th and early 20th centuries. Disclaimer that I am a final year undergrad, but everyone really knows everyone in the department, and for your questions about the MA, I can speak to the experiences of my friends!
Yes, I know everyone you mentioned very well! Dr Rough is great, he specialises in 19th-century British art and the culture of the music hall; Dr O'Rourke works extensively on intersecting histories of art and science in the 18th and 19th centuries; Dr Kouneni works more on classical and Renaissance art, but she does look at classical reception into later centuries, especially through topics like the Grand Tour. If you're at all interested in 19th-century French impressionism/post-impressionism or women artists, Professor Linda Goddard is wonderful as well. To my knowledge, you're assigned a supervisor for your dissertation, but you can specify a preference - either way, the school does well in matching you with someone whose research interests overlap with yours.
The entirety of the art history community at St Andrews is very tight-knit, but I think the grad students are even more so. There are dedicated grad seminar series in addition to the research seminar series each semester, and often visiting Global Fellows will meet with the grad students – all of these provide great connections in academia. You'll have access to a number of great facilities like the university Special Collections, the postgrad college building, the beautiful dedicated postgrad library Martyrs Kirk (with heated desks - I envy y'all so much!), and often certain modules will go on field trips to museums and galleries in Scotland (or even further afield) or attend conferences in town or elsewhere.
The Louvre summer programme is definitely competitive, as students from all three MLitts in Art History can apply for it, but it's really a one-of-a-kind opportunity, as the École du Louvre normally doesn't offer teaching in English. It isn't running this year because of the Paris Olympics (you do need to sort out your accommodation), but it should be running again this coming year.
I will be honest and say that St Andrews is not the most well-connected place to live in, compared to Edinburgh or London. Housing is not the best, with some students living in other villages around St Andrews, or even Dundee for the sake of affordability. We don't have a train station in town, so you'd need to take a taxi or a bus to the nearest one in Leuchars. It takes a couple of hours to get into town from Edinburgh to Glasgow. But the galleries there are great, and the bus is decently affordable (free for under 22s and there are student ticket deals).
I hope I've answered your questions! St Andrews is a gorgeous place to live in, and the art history department is absolutely wonderful, not to mention ranked as one of the best in the UK. So if the idea of studying in a research-focused department with intelligent and supportive academics, surrounded by the north sea and medieval ruins sounds appealing to you, I'd unequivocally recommend St Andrews!