1. Is the pottery clay, muriate of potash and dolomite still considered to be beneficial ingredients?….My Questions:
YES, they are foundation of MTS. You can adjust based on the soil you use. Aaron's recipe is used with the cheapest Top Soil you can find. If you start with higher alkaline soil adjust as needed
2. Have the ingredients in Ukamikazu's recipe proven successful? I already have Azomite and plan on using some. The recipe seems pretty comprehensive but is all the fancy stuff worth it?
I've read that thread. The best person to ask would be Ukamikazu. I've not followed that thread since I posted on it. I don't know if his theories were ever tested in multiple tanks.
3. In a dirt setup is the high CEC gravel considered to be essential? I already own 3 bags of eco-complete I plan on using for a cap and I considered pool filter sand, more EC, or safe t sorb to mix in to make up the rest of the cap. If CEC is not essential than the PFS seems easier to work with but i'm not sure it will mix well with EC.
I've never understood the concern over CEC of the CAP. The roots of plants dig fast & deep into MTS and feed there. I use PFS, and YES I think it's the best CAP, after experimenting and reseaching gravel failure in friends tanks.
4. Will this low organic, rocky clay topsoil be suitable or is a more organic rich topsoil going to be more beneficial?
I use the cheapest Topsoil I can find at HomeDepot $1.17 a 40# bag. The thing to keep in mind is some Organics added to the MTS helps the process of nutrient uptake by the plants roots as that organic materiel breaks down. I ad a small bit of Worm Casing to the MTS when I set up the tank.
>>>Best advise, is take guidance from people that Actually use the substrate you are interested in. There are many people that go years without adding root caps to there MTS substrate. I just recycled 3 y.o. MTS into a new tank.
Don't over analyze it, we are talking about dirt. We kept aquatic weeds, that thrive in third world drainage ditches, fertilized by Water Buffalo POOP. This ain't rocket science.
Best of luck with your new tank.