Getting non tech people to use bitwarden

Not to long ago, I started using bitwarden. For the most part, I like it. Except for one part and that is autofill doesn't seem to work on some sites, well maybe not work isn't the right way of saying it, but has to be done different. On some sites, I will click in one of the login fields and the account info from bitwarden will show up, just click that and it will put the info in. But on other sites, I have to use the fill option in the bitwarden extension. Does it make a difference what browser you use when it comes to this?

I am in the process of getting my parents to use this. First will be changing their passwords to something much stronger. And this is my main question for this post. My parents aren't the most tech savvy, I do think they will be able to learn it, may just take a while. For all their accounts, would they be better off using random passwords say 14 characters long or a passphrase that is lets say 5-6 words long. Both would be random generated. I was thinking passphrases in case they ever have trouble with bitwarden, whether it be user error or something wrong with bitwarden, a passphrase would be easier to type in manually. Either way, will have a physical list in a secure location. I worry they will think using a password manager will become an inconvenience having to deal with a master password even though that should be the only password to deal with.

One thing I should mention is generally both will be using this on pc. At least right now, no plans of using bitwarden on a phone. Don't do a lot on phones. Not to say they will not in the future but not at the moment.