Why buy those when you can make them yourself? It appears they are just O+ stuck in capsules. There are several threads on here on how to source and make them yourself. I don't think the capsules are really needed. If you bought a set of aquascaping tools (which you should, because they are useful) you'd have the long tweezers and could place individual balls under roots of plants.
I used that type of root tab, made it, loved it, then lost my love for it. The little balls start showing up in your tank over time and they are too heavy for a gravel vac and to light to grab efficiently. Your other option is to make your own mineralized soil root tabs which is arguably better than either API or O+ root tabs.
Now I use the API root tabs.
I wouldn't buy Excel unless you want to keep paying for the name on the bottle. On a 75 you'll be money ahead buying the gallon of Metricide 14 off Amazon. Even the WetSpot has their own dark bottle of "Excel" if you want to support a local product.