If wallet1 has 10 transactions, wallet2 has 10 transactions, wallet3 has 2 transactions are they linked to the same user by zkSNACKs or it's 22 anonymous transactions which zkSNACKs can't link to the same user?
Technically, they shouldn't be. Wasabi uses block filters, and they say that each relevant block is downloaded over Tor from a different node, preventing any one node from learning about which addresses are being queried by the same user. You can of course improve on this by linking Wasabi to your own node. Whether or not Wasabi are gathering data elsewhere I can't comment as I'm not going to read every line of code for a product I'm never going to use, but I wouldn't trust their word on literally anything.
Do zkSNACKs store any data to link users from received<>sent addresses after mixing?
We don't know and they won't tell us.
Which info does zkSNACKs share with blockchain companies is it limited to scanning incoming mixes for analysis?
We don't know and they won't tell us.