Hi! I wouldn't recommend reducing it too much, as if someone were to do it on a huge database, it could cause a bit of lag in that area.
I think the beauty of this plugin is that it gradually improves, rather than improving the entire database quickly or immediately.
Or at least not less than 0.5. Try it yourself; the server won't freeze in any case, but I do recommend checking the FPS in Grafana if you have it.
1.0 is ideal if you want it fast and there are no issues.
Regarding the Gingerbread Skin, it's a free skin, not a paid one, so it's safe to use. The game offers it to everyone during the Christmas season.
The same applies to the outer ice wall: it's not a tradable item on Steam or a Twitch drop, so legally it would be exempt from these restrictions.