The systems I saw were more simplistic and voted any post the user posted.
My issue was that often a lot of the content they create is excellent and worthy of an upvote, but many people make shorter posts, and this logic still applies a big vote to it.
Yes, that is the 'fanbase' feature in hive.vote (and other bots that I presume do the same thing). There is also a 'curation trails' feature in hive.vote. A curation trail simply follows some other account's voting pattern. As long as the curation trail accounts you subscribe to are manually curating, then your auto-voting does not distort the manual curation process (but actually amplifies it). This effect is also done indirectly via delegation pools, where you delegate your voting power to a curation account, then that account shares back with you a portion of the curation rewards earned by the account.
My main concern has been with auto-voting bots trying to snipe the non-linear rewards associated with presumably good posts. In the process of doing that, they ultimately muddy the manual curation waters (as can the 'fanbase' bots you mentioned).
Alas, with HF25 linearizing (mostly) the rewards curve and expanding the 'early vote' window from 5 minutes to 24 hours (or maybe 36 hours), that will remove the incentive for auto-voting bots to vote early (and will actually incentivize them to hold their votes until just before the 24hr (or 36hr) threshold ends.