is it okay to have a subdomain to connect to vaultwarden?
A lot of the people would disagree but I think so, yes. Provided that you have set up all the security measures such as firewall/fail2ban, you’ll be fine.
Am i better off just trusting bitwarden and sticking with them?
I think of it as a matter of personal preferences. But honestly, if you had to ask this without your own basic plans for security, I’d advice you to stick with Bitwarden. You’ll just sleep better, that’s all.