Hello,
The fish store advice are usually revolving around them selling stuff to you. Forum and experience advices will be genuine and even if conflicting advice in forums/experiences aquarists, it is unlikely that either of them will be incorrect or wrong. The problem occurs if you follow one path and then trodd on to another and then a 3rd creating a mess. So whenever you get any advice, dont start working on it immidiatly, wait for a few more people to pool in and then decide what you want to do and stick by it.
Once you are setup and cycled, it should be a breeze. Its these early stages that causes mayhem and confusion so once out of it, you will start understanding the fish yourself.
Dont worry about hardness or PH unless you want to breed specific fish or if you want to keep overly sensitive fish like discus etc. Most fish will aclimatize to your water parameters well and playing around with hardness or PH usually leads to the stressful side of the hobby.
And, sant does not reduce hardness. It may increase it but certainly not reduce. Ion exchange, PH buffers and precipitators, dilution with RO water or softer water, are the only way to reduce the hardness. There are a few more ways to reduce PH like Peat filtered water along with the above methods but frankly, they are not worth if if you are interested in keeping community fish.
Nim