Acidic is lower than 7, alkaline is higher.
Acidic pHs are normally associated with low KH, and alkaline pHs with higher KH.
KH often, although not always, runs alongside GH. Soft and acidic normally go together, hard and alkaline normally go together. Your water softener isn't really related to this. It doesn't effect KH, so it won't effect pH.
Generally fish will adapt to waters that are somewhat outside their ideal conditions. A stable pH is more important than a proper one. You should know what you've got and watch for changes (in all three parameters), but its not critical that you be spot on this or that.
I like to keep fish that are suited to my water, but plenty of other folks stretch things a bit without apparent mishap.