What's the distinction between fantasy and discovery, here? You can't really engage with a fantasy world without exploring it - even engaging with an NPC is an exploration of the world. (You can be a completely RP-less hack-and-slasher - and that's fine, to be clear - but that would mean neither fantasy nor discovery, more like challenge.)
Fantasy is the act of imagining itself--of conjuring mental images or sensations, of engaging in and with the depiction of the conceived world. It is nourished by lavish descriptions and evocative dialogue.
Discovery is the act of
learning about the world. You don't need to have a crisp, practically-there "feeling" of the world in order to learn things about it and expand your horizons (e.g. visit new places, uncover hidden things, witness rare or unusual events, etc.) You just need to gain more information or find the answers to questions or go to a new/rare/distant place.
Now, many folks who like the one also like the other, but that doesn't have to be the case. One can read mystery novels, for example, without having any particular interest in or appreciation for evocative wording or painting a picture in the reader's mind; the process of
solving the mystery is the key focus for many mystery fans, and that's practically pure Discovery. In a more videogame context, Minecraft can offer tons of Discovery with very very little Fantasy, because the world is intentionally minimalist, blocky and unrealistic, but delving into the earth in search of treasures or slowly learning what kinds of things can be built is a Discovery motivation.
Conversely, I would call Dragonlance (and many other "scripted" type things) heavy on Fantasy and light on Discovery--this isn't always true (I hear Zeitgeist is pretty heavy on Discovery and Fantasy both), but often. To give a different example, many MMOs specifically target what is called "class fantasy," that is, supporting the ideas, themes, tropes, etc. associated with a particular character class, as an important aspect of play. If playing a Paladin doesn't evoke enough Paladin-y elements in the imagined world (e.g. righteousness, zeal, golden glows, shining armor, horsey friend, etc.), then that class is failing to live up to its "class fantasy." If the Paladin
does do that, though, there's probably not going to be any "discovery" involved--the player will know what Paladins do and how they work as a matter of course, they will in fact be
expected to know those things and be taught them in a reasonable way, removing most of the interest behind Discovery.