What does skill max mean?
Similar to spiritual and hermetic spell maxes, your skill max determines how high you are able to train in any skills you aquire. Unlike spells, skills are all grouped into one category. So if you are a giant, which has a skill max of 100%, and a fighter, which is a non-magical guild, you can train any of your skills all the way up to 100%. If you were a giant and a cultist, which uses spiritual magic, you would be able to train your non-religious skills to 100% as well.