The ones with the chocobo are only legal in a casual format known as EDH as well as Legacy and Vintage (the almost-anything-goes formats). The ones with the non-chocobo symbol will be legal in every format. There are often more than one card designed per character, to around upwards of six for
hispanic/mongolian Gandalf, but the vast majority of these cards are completely unplayable in competitive formats. Instead, the point of a card like Y'shtola there is to be a Commander: its colors determine the colors the deck is allowed to use, and you generally build around the activated effect in some way (like, for example, using
this card to ensure a draw on every player's turn).
Somewhere in the non-chocobo-symbol set, there will be 1 or 2 stupidly designed cards that are laughably overpowered and absolutely fucking stupid enough that they become wildly-expensive 4-ofs for competitive decks. The One Ring (until it was banned) and Orcish Bowmasters are two standouts from Lord of the Rings that completely warped an entire format by their inclusion, though you could at least argue that the art style + overall theming loosely 'matches' a fantasy TCG. Final Fantasy is certainly closer than Doctor Who, at least.
The commander cards also don't tend to be particularly flavorful (for whatever reason). Compare this to the mainset:
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Final Fantasy 14, 13 reflections + the source -- there's something more to it, at least.