It's less "if I'm fine with both he/him and they/them that must me I'm not cis" and more "I really dig the idea of being nonbinary/whatever non-cis identity because it resonates with how I understand my gender"

Like, you can be cis and use he/they if you want to. You get to decide what you vibe with. Try pronouns and clothes and identities on. Do a mental identity drag show. Be messy and weird and look at things upside-down and backwards on occasion. Experiment.

You're the authority on you. Nobody else knows you like you do - so try it all, then come back and let us know what you found out!