I don't recommend Apple's keychain. It's smart enough to track usernames and passwords and feels very satisfying to use on an iPhone, but doesn't capture some other parts of authentication. This includes security questions, OTP, capturing notes around how sign-ins can be weird (HSAs and other portals rife with redirects), and non-iOS devices (as well as non-safari browsers).
Bitwarden is fantastic. I pay for the OTP features, though I feel keeping the codes alongside my passwords weakens my security posture. That's my choice, though.
I've used iCloud Keychain for all my personal stuff since it existed. It's pretty bare-bones, but the built-in integration into Apple's software makes it a no-brainer for me. It's worked great!
The most valuable parts of 1Password for me are storing non-password stuff like license keys, secure notes, random security question answers, and the like.
I’ve always used secure notes in the Keychain app for this. Not as smooth as 1Password, but it does the job when I need a licence number (when I get a new computer, so once every ~3 years) or an answer to a security question (can’t say how frequent that is; certainly not more than 1 every other year).
I’ve been doing that for more than a decade (more like 2 actually) without a hiccup.
Never had any reliability issues with iCloud Keychain since switching over 2-3 years ago, but obviously it's less featureful than 1Password. I liked how 1Password had a dedicated section for software licenses, but now just use a Notes note for that.
My daily drivers are a MacBook Pro and an iPhone, but I'd go with a 3rd party password manager every time for the ability to access passwords on a non-Apple device if I want.
I've recently been using keychain for new accounts, but not sure I wanna bite the bullet and go all in - just need a nudge.