I have noticed Candytuft spreading to different places in my yard. Is it considered an invasive or is it okay?
Candytuft (Iberis sempervirens) is not normally considered invasive. It may be especially happy with the conditions in your garden, and it should be fine to continue growing it, unless you dislike its proliferation.
Here is an information page about this plant from the Missouri Botanical Garden website. Note that it says: “Stems may root where they touch the ground creating new plants which can be left as is or transplanted to other areas.”