The right cube really rewards people for picking up
Daze.
I tend to like Memory Lapse a lot in non-blue decks and decks with things like venser and clique in it, but I can agree that there are better options, I just like what a hard wrench it throws into the works splashably, and more or less whenever you need one.
I'm sure everyone is already sick of hearing about this but when Eric was complaining blue's counter suite had gotten a little dull, I was giving him this advice (Eric cube's modern)
Swap the existing
Rune Snag (x4),
Remand,
Condescend for
Remand (x2),
Mana Leak (x2),
Condescend (x2)
I really like remand, it's like rarely not netting you tempo dollars, even when you are just trying to cycle it. It reminds me a lot of miscalculation, kinda better against late game plays though.
I really like condescend but I don't think it's amazing in most people's cubes.
As to the question how many? I'd say try to fill out the two slot before any other. 2cc counterspells are sort of all pretty moderated these days, but they all feel a lot better than drafting a 3cc one. Fill out your blue staples and then see how much room you have for spells that don't influence what is already on board.