Only for a test, I do not see myself switching to passkeys any time soon, using KeePass is fine in my use case. If there would be some site for which I would need to authenticate every day I would probably create a passkey on device itself (Windows Hello or Google Password manager) since authentication speed increase is undeniable.

Only authentication method changes, there should be no difference after you sign-in, how long sign-in is kept still depends on site owner.

There are various sites to test authentication experience, here's one where you can test it with dummy account and no registration https://webauthn.io/. It is pretty cool, but you need to create a passkey for every site on all devices to fully utilize their potential.

I’ve had them since 1Password beta. They do not change the duration of a session unless the service opts to. In the case of google they ask me to log in more often, presumably because there’s less friction, so why not?

I use passkeys for some sites, but have been reluctant to go all in until I'm sure all my devices can support them. I'm not always going to have my desktop with me, and likewise my phone's battery can be flat, etc. I've always wanted passkeys to first sync across all my devices, and ideally to be exportable and brought into a different service. Right now you can export your 900+ passwords, and import them into a different service if you want to move. You can't do that with Apple or Google passkeys.