Using your example and the premium Search Tweets: Full-Archive endpoint, you could get the Tweets and retweets matching the hashtag, but the user data for Search is updated at the time of the request and would not be a snapshot in time for their followers at the time of the Tweet. (Historical Powertrack does have a user snapshot, but the Search does not).
Also, if you didn’t want retweets, you could negate them:
Query: #aliens -is:retweet
fromDate: 2017-01-01 00:00 UTC
to date: 2018-01-01 00:00 UTC
maxResults: 100 (or 500) per request/page of results
Assuming that there are over 500 Tweets per 31 day period and the results would be saturated, you could get
50 requests X 100 tweets = 5,000 Tweets for free using the sandbox only
100 requests X 500 tweets = 50,000 Tweets for $99 at the first tier
up to
2500 requests X 500 tweets = 1,250,000 for $1899
In the last ~6months, there have been
~200K tweets matching (#aliens)
~ 98K tweets matching (#aliens -is:retweet)
So you would probably want to make your filter more specific to reduce the noise and improve your search efficiency.