I disabled Authors (too many feeds otherwise) and put blog@domain.name in the ActivityPub settings.
All messages come from the blog, it looks good in the Mastodon profile and I think that the doubled domain name looks kind of funny.
Only disadvantage so far is that Mastodon shortens the user name if it is mentioned in a message. So it appears as just @ blog (without the space).
But you can e.g. also choose your name or something else.