I find when world building there is a delicate balance between thoughtful planning and allowing yourself to be guided by creativity. I quite like the process of creating a game setting, and it is one of the reasons why I am more partial to science fiction than fantasy (I just like the way science fiction writers build worlds). But I think as gamers we can sometimes take world building to cult like extremes and forget it is just a tool and these are just games. Ultimately as a GM or as a designer, you need to find an approach to worldbuilding that works for what you need at the table. For me that means striking a balance between the desire to research and create something plausible and the need for something fun and playable at the table. I want roots but I don't want them to become chains that limit my imagination during play or scenario design. By the same token I want to explore plenty of source material for inspiration but don't want to be tethered to it either, merely regurgitating facts cloaked in fantasy.
This is not an easy balance to strike. For me research is not only important, it is essential because it is a source of inspiration. But research is slow and time consuming. You can always look for summaries online or visit wikipedia. I don't care for this approach though. I like to give myself time to go over plenty of good sources and build up a strong foundation.
At the same time, I don't want simply to recreate the material I've read. I want to produce something new and I want there to be room for going with my gut and adding things that just feel like a good fit.
I find it is a constant back and forth between in depth research and then shaping that into something workable for the setting.
With Wandering Heroes of Ogre Gate I am working hard to respect the source material but fit it into the existing Sertorius cosmology. I'm also trying to strike a balance between the historical sources and the conventions in the genre (which are not always on the same page).
This is an enjoyable process but I also have to step back sometimes and give myself permission to create rather than emulate. The trick has been to make sure what I am adding doesn't take away from the wuxia genre aspect of the game, but rather contributes to it.