I was gonna write a big old post on this but I didn't, so here's the cheat list of stuff you need to know about tweaking character creation:
1) Classes will only load if they have distributed exactly the number of points assigned in properties.lsx. Thus if you change NumStartingAttributePoints from value=5 to value=6, you will have to go into each class preset and add an attribute point if you want it to work. Change it to 0 and you will have to go in and remove or set to 0 all the assigned attribute points.
This is also true for talents and ability points, keep in mind that it costs additional ability points to raise an ability above 1.
2) Anytime you change a node with a "handle" property, such as ClassDescription, FemaleDefaultPlayerNames, or ColorName, you need to change the UUID or it will always point to the default text description and your text changes won't be visible. The 'correct' way to do this is to generate new UUID, but all you really need to do is change one or two numbers.
3) If you use the armor nodes, Classes can only receive armor that is defined in properties.lsx. If you put the armor in their equipment set though, everything seems to work just fine. I don't really understand the purpose of the armor nodes.
4) You can change FemaleRootTemplateIDs and MaleRootTemplateIDs to any character in the game (troll, skeleton, statue), but you'll lose basically all visual customization. Also this switches your roottemplate on clicking male/female, I don't know if it's possible to change it on class selection.
4a) There's a 'race' node and in theory you could add more races, but the game's GUI doesn't seem capable of handling it at the moment.
