Applicable to strategy games where the player is in control of single squad (or few small ones). Usually these are squad tactics games.
Requires that single player is in control or lead of multiple characters (excluding other human controlled characters). So this is not for MMOs where you can form a party with other players without having those additional characters.
Pets do not count unless they're represented as actual characters by the game (not tied to the existence of the actual player character).
Usually groups have the added benefit that you can't truly die unless the whole group is wiped out, though sometimes it is enough that the protagonist dies (though this is usually the case when you can't directly control the others).
About Group (Squad-based;Party-based)
I think that this tag does not apply to games such as Final Fantasy X. You're in control of a squad when you're in combat mode, otherwise, you control a single protagonist. If this tag applies to FFX, then it should apply to most console-type RPG.
The protagonist is pretty much always recognized as "the leader", which you primarily control. The tag is NOT for what multiple protagonists and collective are for. And yes, it does apply to many console RPGs.
Who is the protagonist in the 1st Final Fantasy?
I don't know (I've never played it and likely never will), but if it's unclear or you always control a group, then isn't it a clear case of multiple protagonists? Group tag would still apply, though, since that's what it is.