Do you have a RPG in mind that exemplifies both?
I think there is a tension in design here, myself. "Flavour", or narrative-driven imagining, is liable to be disrupted by too much prominence of fiction that disrupts it, and so is best supported by a strong degree of curation - typically GM curation - that can help mitigate any such disruptions and keep what happens at the table at least broadly in line with what the description has evoked.
The GM-side of this - to continue my undead example - is to encourage "good roleplaying" by players who have had the GM describe a scary undead to them.
Conversely, the 4e-style approach, in which it is the actual play and resolution of things at the table that generates the imagined stuff, relies upon robust mechanics with non-curated outcomes to do its thing.
This is why I don't think it is easy to do both. I mean, maybe you'll get both from time-to-time, but I don't think it's easy to design to achieve both as consistent aspects of play.
