Just to be clear, this is the
planetary romance genre (also known as
sword-and-planet).
Planetary romance, by almost every definition, doesn't include stuff like
Flash Gordon, Buck Rogers, or
Space 1889.
Differences are that usually in planetary romance:
- the voyage to the other planets is usually of little importance or significance
- very little attention is paid to the scientific plausibility of the setting
- the emphasis is on swashbuckling adventure and high melodrama
- the protagonist(s) usually have no choice but to go native
- often, the protagonist(s) become more at home in the alien environment than on Earth
There's no reason GMs and players can't add those elements into the book I'm writing, or emphasize the aspects that are there, but I want to be clear on what I'm writing to prevent people from thinking it'll be something else.
More loincloths and jeweled battle-harnesses than redcoats and Sharps rifles... if that makes sense.