Rules consequences of dragonborn not being a template?

[MaxiDuRaritry]

...but you can't be two races at once.

The fusion power does this, and certain other options (mostly spells, such as alter self and magic jar), doppelgangers (especially the more powerful variants, such as ethereal doppelgangers), hagunemnons, and (to an extent) illithid savants also do this. You keep some racial traits and gain others, occasionally (but not always) losing some in the process.