Just some data points:
I'm now month 2 into my redcard in Lakewood, and it's great. CS or cashiers at Target on 70 are super friendly and super helpful. Nobody has ever asked me for ID or given me a problem with loading 2 redcards at a time.
I did get flagged for fraud from Amex one time. They refused to clear the fraud alert by phone from my cell, and insisted I call from my home phone to clear the alert - stupid waste of a trip to Target (though I always carry multiple CCs I'm aiming for bonuses on, I specifically wanted to do the Amex on that trip). I've asked them to given me 10k MR points as an apology, and they said they will do that only after my first statement posts.
My friend, OTOH, has been having a lot of issues with Chase. They flag his card every single time he tries, even if he's cleared it in advance. Now they say he has to take it into a Chase branch to clear the fraud alert.
My only concern here is whether Amex will think it's suspicious that I have so many large transactions at Target, all in such unrealistically round numbers, and flag for FR? I guess nobody can really know for sure