As for why we use 1Password instead of iCloud Keychain: my spouse and I are routinely tasked with helping my MIL log into sites, so we have set her account to default to saving to a shared vault we each have access to (we have a separate 1Password family account to share between my spouse and I).
We briefly tried a Yubikey and other biometric options and ran into what is apparently a common problem for elderly people: she has barely perceptible fingerprints. She could not use Touch Id on her iPhone when that was a thing and cannot reliable use it on her 2022 MacBook Air.
I hate to say this but shifting to a long, memorable passphrase (reused across sites) coupled with a second factor may be more useful for an elderly user.
If not, I'd recommend 1Password for the ease of use, the good track record, and the great support for all platforms and browsers. Pricing is IMO reasonable as well.