The stores will vary.
Even if you have a retailer chain that works with Curbside pickup in some areas, it will not be guaranteed the one near you will be on the list.
It seems fairly selective, and it's basically varies by region of which stores will be on the available list to choose from.
Gift cards are also not eligible for this offer. The way Curbside works is that they have a preset list of items you can purchase from if it's at a store that's near you. It's not the full selection of inventory, particularly for games, which is a meager selection at best. Inventory of eligible products will also vary by location of store.
The offer is good for returning customers, in fact, the email actually puts in the detail that they haven't seen you in awhile, so definitely not a new customer offer, and I also used my code already, so there's that.