Truth be told, this would be the second SLA I've ever been to. The first was last year, also in Glasgow, and at first, I thought I was unable to watch every film in the Glasgow line-up due to timing (I had meals to consider) and, for certain titles, not checking out any connecting series/films, but I worked my way around it and watched all of them. Out of all of them, there are two that I would probably need to check out their respective series in order to familiarise myself with the story and/or characters.
Regarding the Kitaro film, from what I've read, it's a prequel to the 2018 series, which I can stream on Crunchyroll. As for Lupin III: The Castle of Cagliostro, I haven't seen anything Lupin III related, and I would like to familiarise myself with the characters beforehand. Most series I can stream on HIDIVE (except for Part 4), but I don't know how much Lupin III material I need to watch.