I'm not especially familiar with the stations that have been mentioned other than Tokyo itself; but presumably limiting the number of train changes would be a good idea, since you'll likely need to change platforms. The Chiba routings would require at least two changes; the Keisei Sky Access-Musashino option that I found on Hyperdia seems to be the only one-change option. In particular:
- A Keisei Sky Access train departs Terminal 1 at 7:32pm; its sixth stop is Higashimatsudo at 8:12pm
- A JR Musashino train departs Higashimatsudo at 8:17pm; after the first stop (Nishifunabashi) it runs on the Keiyo line and its fourth stop is Maihama at 8:40pm.
But if you are willing to spend the money, using a taxi for the final leg is likely to be the easiest option, since you won't have to catch a hotel shuttle or the monorail at Maihama. I recently opted to take a cab from "downtown" to the Tokyo
Disneyland area because I didn't want to deal with a pile of baggage on trains.
Although I've usually found customs at Narita to be efficient, a 9pm arrival time at Maihama based on a 7:05pm flight arrival might be ambitious. I'd suggest checking later times on Hyperdia to have some back-up options if all doesn't go according to plan.