IME I always get better plant growth with a good CEC soil. However I still get good growth in fully inert sand/gravel. It's just the difference between thinking it's looking lush and actually looking lush.
A little like thinking your water is crystal clear, then putting Purigen in and realising it wasn't
I use Tropica basically because I am tight and I bought it 5 years ago. I reuse it each time. Tropica has no nutrient in it but has high CEC so it draws nutrient in.
I have used Kitty Litter before and it worked fine but not as good as with the Tropica. Am currently use it in my little 8 litre (can't really take any observations from a tank that small, plus I tend to neglect it a lot.) I only used kitty litter in that one because I wasn't going to pay anything for the content of that little tank and I had a bag of kitty litter around. I did top it with gravel though because it breaks down very easily.
From what I remember (I think I read somewhere but can't remember) that kitty litter does have high CECE but nowhere near the decent soils and miles behind humic soils. this would go along with my observations really that kitty litter is better than totally inert but short of the expensive soils.
This is why I put a thin layer of Leonardite underneath my substrates. Read it on Barrreport and seems to work a treat
Saying all of the baove many people use plain old sand and dose the water column religiously and are very happy with the results. Don't know if they have used aquasoil or one of the other variants from other brands to compare with so it may be a case of the 'purigen' comment above.
If Florabase is made at the same place as Oliver Knott's then it is rebagged 'contra-soil'. This is the Japanese brand name. Then they bag it up for different clients

Most of what you get is made by this company or one of the others in the region. And of course if they sold Contra-Soil without being rebagged over here it would be circa £14 a bag. lol. But they don't more's the pity.
On the Ops question similar to Ian I just set up a scape. don't worry about anything, plant it up and in with the fish/shrimp. Although I would advise to follow Ian's instructions above r.e. daily water changes for a couple of weeks I don't

I just start up a scape, plant it heavy and then immediately continue as if it had been up and running ages. Cherry Shrimp are hardier than most fish IME

Very hard to kill off. They even survive without acclimitising if you just transfer from one tank to another. Not really a good indicator of whether your fish would survive IMO.
My summary o the above. I use the Tropica because I have it. If I needed to replace it yearly then I would probably just go inert rather than use kitty litter. Makes a mess when you have thrashing Corys and non stop fiddling m,as colonies of shrimp. lol. No science behind it for me though. I don't spend ADA nor Florabase money on substrates. That money is better in my pocket or buying fish/plants/baby clothes. lol. So I am with FishyJake on this one

I think just using a little Leonardite for the stupendous CEC may well be the key in my tank rather than the Tropica.
Why do these high CEC have this 'negligble' better growth? I think it may be more a case of stabilising the levels rather than anything else. The pulling out of the water any 'spikes' the plants don't use and then releasing for the plants when there are troughs.
On the 'spent' time part. If you don't dose and rely on the substrate then you saved on the fertiliser so it levels out really (assuming you buy the fertiliser rather than DIY) If you do dose religiously it should continue for eons (I would've thought.)
On the lean dosing part. A lot of people 'unknowingly' lean dose. If you use TPN+ or Flourish then you are lean dosing. Would take a lot of the stuff to go EI levels

I've used PMDD+PO4 lean dosing before. Worked a treat howeverI like to use EI because DIY ferts are cheap and it removes any worries. Lean dosing can leave you defficient sometimes when you are a lazy pruner such as I
Andy