2, 2.25, and 2.75u keycaps all use the same common 2u stabs, so you’re good there unless you really need 3u for some reason.
I buy from AliExpress all the time. I’ve always had good luck getting what I order, but the cheap shipping options can take a few weeks to arrive in the US.
Aliexpress is in the same vein as Amazon - the site itself has no bearing on whether any particular vendor is reputable, but a majority of them are. KPRepublic is a good vendor for sure.