I wouldn't be faster in multi or single, it would faster based on the player doing the reaction. Some players take a long time to decide on actions, this slows down time while playing, add-on a pop up window for reactions and it stops combat and waits for the person to answer the box.
What's your alternative to a pop-up reaction system? The toggles we have now? While this doesn't have a large time effect right now in BG3, higher levels and the implementation of more reaction-heavy classes (e.g., spellcasters' counterspell, Bards' cutting words, Paladin's spell slot smiting) will make this toggle system more time-consuming. Especially for resource-consuming reactions, where players will hem and haw about possibly committing a high level resource (e.g., 3rd level spellslot for counterspell or smite), when the auto-reaction system might use it on a cantrip or 2-hp enemy.
For a specific example, let's use Paladins' smiting.
- Using a toggle reaction system, every turn Paladin players will need to decide what level (if any) Smite to toggle on for application to an opportunity attack.
- Using a pop-up reaction system, the player needs to make the same final decision (what level smite to use), but only in cases where an opportunity attack is actually provoked and the player will know what enemy they're attacking and thus won't need to consider things like the possibility of wasting a high level spellslot on a 2-hp enemy.
So unless Larian dumbs down the toggle reaction system (e.g., Paladins can't smite on reactions, or maybe they always smite on opportunity attacks using the lowest/highest spellslot), toggle reactions for Paladins will end up taking a similar amount of, if not more, time over the course of the game. Just that the time will be spent during players' turns as opposed to between enemy turns. (Though yes, I acknowledge that pop-up reactions can significantly slow the game down if the player leaves to get a snack after their turn ends.)
Possible solution: a mix of toggle and pop-up reactions. Basically, you toggle which reactions the game should ask you about (e.g., opportunity attack, counterspell, smite), and then when/if that situation occurs you also select how/if to use them. For my spellcasters I'd always have "opportunity attack" toggled off, so the game would never bring a pop-up for this. And the toggles never commit you to using a resource, so turning them on/off during your turn will be a much quicker decision.
