I have created a category and added several new field types. I have also created several subcategories and would like to use the same new field types in those as well. Is there an easy way to do this, or am I going to have to manually create all those again in each subcategory?
To apply extra field types to the children categories you need to ensure that the subcategories are already created and you can then use the APPLY TO ALL CHILDREN FEATURE to apply them to the children of the parent cat when you create the extra field. You can not go back and retroactively apply to new subcategories you make after you create the extra fields.
No sorry not with the arrays and how it stores those additional extra fields. You need to remove the extra field and then recreate it and use the apply to all children checkbox to acheive that or do it for each category.