I used to use the BRS chems some years ago. IMO, they are really all the same and don't make any difference in your tank, except BRS has REALLY GOOD marketing.
It's kinda like all these DC pumps we're buying that all look the same - they're all made in the same factory. They just use a different colored plastic, slap a different sticker on it, and tada! New pump.
When the Canadian dollar was strong, then buying the BRS stuff made a lot more sense. Now the savings aren't really there unless you're buying the 5-gallon pails - even then I'm not sure once you start adding shipping to 5-gallon pails. BRS charges 15% for Canadian duties and taxes to all orders, then you have to add 40% right now for the dollar (thanks to Trump for the soft wood tariffs). Then you pay shipping (in US dollars) on top of that. It really adds up right now, and I'm not sure why people are still shopping in the US other than habit.
The Aquaforest KH Buffer is $47 from Reef Supplies and free shipping over $149 (BRS doesn't do free shipping to Canada). If you want to use "soda ash" (sodium carbonate), then bake it in your oven at 350F for an hour and you have soda ash. Or just buy the Reef Supplies soda ash.