If you are writing via planning and worldbuilding, your creative process goes like this:
idea => concept => detailed plot/setting
Research can be (and should be) used in every step of the process. Your methods #1 and #2 seem to imply that this research should predate the "idea" step and should be a source of inspiration. I can not really suggest anything there. Anything that gives the writer new ideas is a good thing, but this is highly personal.
A different kind of research is needed when an idea is developed into a concept, and then concept serves as a stage for specific plot developments. Obviously, you would want to avoid any holes in concept and in plot, and likely want to avoid any striking similarities with existing stories. So, after you have your idea, #1 question is
Have this been done before?
If you are well familiar with your genre, chances are that you immediately can pinpoint other works where something similar had been done. Anyways, it would be good to do some Google or TV Tropes search to see how original your idea really is. The outcome could be different:
- Looks like my idea is very original. Hooray!
- Other people have done similar things, but my idea is really
- My idea is not new at all. Duh!
Even if your idea is not new, that's not necessarily bad. In fantasy genre the setting is important, but the story is the most important part. You may use cookie-cutter elves, dwarves and dragons if you like. If your story is original, it would be perfectly fine. Conversely, if your story is a collection of well-worn tropes, fresh and original setting may not be enough to save your book.
If your idea is original enough, the next question is
Does this concept make sense?
As you flesh out your world, you need to understand how this novel idea would work out in everyday life. It's easier if the idea is not very novel, because other people have already done the work of rationalizing the concept, or supplying some "standardized" magic to make some non-scientific concepts (like flying and fire-breathing dragons) to work without readers asking too many questions. If your idea is very novel, you need to make it work with the minimum amount of necessary explanations. For example, if levitation magic is widespread in your world, it would be natural for different creatures and people to fly. Otherwise, the reader would be striving for an explanation.
I can recommend to get familiar with Brandon Sanderson's First Law, Second Law and Third Law of Magic. Also, other answers have already recommended the sister worldbuilding site where you can find help polishing your concepts.
After you are satisfied with your concept, you can move to the plot. And here lies the next question:
Do I need to tweak my concept to make the plot work?
Here is the area where (imho) most promising, but less than perfect stories are suffering. This problem is by no way limited to the fantasy genre, but it is particularly common here. You need some magic to move your plot and resolve your conflicts, but you don't want it to look like you are inventing new things as you go just to push the plot in the right direction. Again, I can recommend reading Brandon Sanderson's opinion here. It is Ok to encounter new things while on a journey, but it's not Ok to create some reader's expectations and continuously smash them by introducing more and more new things.