Megaplex is a good simple fight with lots of flavourful scene setting.
Bad Chameleon is truly exceptional. Great setting and excellent opportunities for role-play that require improvisation and problem-solving. It also has one of the most chilling baddies I've yet encountered in Starfinder.
River Rat has a nicely balanced starship combat that should let players explore the full rules without getting bogged down for hours.
Nightmare is a great example of using environmental effects and saves to aid storytelling.
The only modification I would suggest is to make the fights a little tougher!