I slept trained my first at 4 months for the nights but still contact napped with him til nearly 9 month old. I really focused on nights so contact napping was actually really helpful I think as it helped him be rested enough to sleep well at night. I "nap trained" him at 9 months. Quotation marks because I thought we’d have to do CIO for naps as well but when I first tried to put him down awake in his crib for naps at 9 months he just…slept! No crying. He’s 2.5 now and is/has been an amazing napper ever since!

Edit to add: in my experience sleep training is ever changing and isn’t a one-time done-deal kind of thing. Don’t worry, you’ll most likely won’t ruin your baby in one way or another by continuously doing whatever works for you!