I'm no expert but, when I found TFP, last summer, I did use the Walmart kit, and the extra HTH reagents I had, until I ran out of reagents and, also, I ordered the separate FAS/DPD from Duraleigh. I did pick up some Taylor CYA reagent from Leslie's as the amount in the Wally kit was so small. I test for CYA more frequently than most people, probably, as I have to backwash more frequently due to our extreme amounts of very fine dust. We also had record winter and spring rain amounts so lots of water had to be let out of pool on several occasions. Then there's the times I over filled the pool, when I was topping up, and forgot the water was running.
I, also, like using the HTH CYA bottle and tube as it uses less reagent than the larger bottle and tube that come in the Real kit. I don't think the Wally kit does Calcium Hardness (CH), just total hardness, so you have to estimate the CH using a simple formula. I think I found that in Pool School.
The Walmart kit won't be as accurate but for me it was close enough until I could gather the funds for the Real Kit. Any kit, with fresh reagents, is better than test strips or testing done at most Pool Stores.
gg=alice