Since you've had a lot of issues with bacterial infections in the past and will be new to higher grade shrimp, definitely go with a well-rounded buffering substrate like Aquasoil. It'll also be great for your plants.
Shirakura Ca+, Mosura Mineral Plus Ultra and Salty Shrimp GH+ are my favorites for remineralization. They're all really clean and will last you quite a while. If you get the 1,000gram container of Salty Shrimp, it'll last you a really long time.