Does the Dragon in the Princess & Dragon expansion ONLY eliminate the standard meeples, or does it also affect, for example, the builder and pig meeples from the 'Builders and Traders' expansion?
Depends which rule set you follow. It always eats "followers" in all rulesets I believe - which is your standard meeple, the large meeple, the mayor and the wagon. It never touches barns. And depending on which way you want to go, it could eat builders and pigs (but if they are ever left alone on a feature without a companion meeple, then they should be removed). It will eat sheep in the newest expansion. I forget if meeples on towers are safe or not.