Hi Allan With Sørensen, thanks for your interest in the feature and your questions!
With respect to your question around whether the recipients get the same kind of sign-up as if they had been invited through AAD B2B invitaiton manager, I assume you're referring to the invitation acceptance flow? If so, the answer is no. This update does not take the user through the B2B invitation acceptance flow. Instead, the experience will be such that if the external recipient does not already have a Guest account in your organization's directory then they will go through the one time passcode experience we released earlier this year (just like before this update). The difference is that after they've entered the passcode, if we detect that they already have an Office 365 account then we will ask them to sign-in if they aren't already signed-in and then create a Guest account in your directory. Once they have a Guest account, they'll never again be asked for a one-time passcode.
If you have configured a link to your privacy statement then they will see that link as part of the one-time passcode flow.
Yes, this is currently only for organizational accounts. We absolutely understand the desire to have the same behavior for Microsoft accounts. We have nothing to announce right now, but hope to share more about this in the future. Please stay tuned!
In general, external users *should* have the same features available to them whether they signed-in to an account or whether they gained access via a one-time passcode. The primary exception to this is the ability to open and edit Office documents using the desktop apps. With that said, I just gave this a try and am noticing that one-time passcode users are in fact unable to create new Office documents in a folder while Guest accounts can, just like you said. Let me follow up with the team on that. I was however able to successfully copy/move as the one-time passcode user. Feel free to PM me with more details or differences in capabilities you're noticing between both types of users.