Polymorph is of course an easy and often only way to add a dragon into a humanoid party, but it has the danger to rob the PC much of its flavor as most of the time is spend as a human. Bayically you would have the same effect of playing some class that can temporarily into a dragon. Also it limits the possible dragons useable as PC unless you houserule.
A pure dragon party works better (Council of Wyrms) but it might be hard to find adventures for such a group.
For a mixed party the setting and the adventures have to be adapted. Dragons merly being exotic than awe inspiring/terrifying helps with social interactions and instead of old ruins and dungeons you should use caves and the open world more.
And for social settings a city and castle are problematic. Villages and things like encampments are more dragon friendly (size wise).
But don't overdo it either. For balance reasons the dragon PC should be faced with less than ideal conditions often as long as he can still participate.
A pure dragon party works better (Council of Wyrms) but it might be hard to find adventures for such a group.
For a mixed party the setting and the adventures have to be adapted. Dragons merly being exotic than awe inspiring/terrifying helps with social interactions and instead of old ruins and dungeons you should use caves and the open world more.
And for social settings a city and castle are problematic. Villages and things like encampments are more dragon friendly (size wise).
But don't overdo it either. For balance reasons the dragon PC should be faced with less than ideal conditions often as long as he can still participate.
