Goblin Queen (She/Her/Hers)
There’s nothing to suggest a two-handed weapon needs any sort of “propping” to be held in one hand.I don't disagree; it's well-settled one can hold 2-handed weapons with a single hand. My issue is whether "propping it" in one hand counts as your free action for the round. Absent a rule, it's pure DM discretion.
Likewise, there’s nothing to suggest that an object interaction is required to grip a weapon in two hands. All you need is two free hands.If so, then for the rest of the round it would affect your ability to take attacks of opportunity because you'd have to wait until your next turn to use a free action to get 2 hands on the weapon again.
That’s correct, in the same way that the second part of crossbow expert is irrelevant when wielding a longbow. The benefit affects dual-wielding, and sword-and-board.If not, the Warcaster Feat, subsection #2, becomes irrelevant when using 2-handed weapons.
None of this is relevant to two-handed weapons. You can hold a two-handed weapon in one hand, in which case, the other hand is free. You can use that free hand to perform the material and somatic components of spells, or grapple, or make unarmed strikes, or interact with objects, or hold the weapon that’s in your other hand so you can attack with it.Also see D&D's 2015 "Rules of Spellcasting" (Sage Advice) page, relating to when your hands are free for casting:
There's a specific rule under Material Components that says when a hand is holding a spell's Focus, you can use the same hand for Somatics, but this ruling is not extended to spells without a Focus. The cross-reference is whether there is a "spirit of the rules" that a restriction applies unless you take the Feat to overcome it.