I would think there would be a big difference between bark which is organic and provides nutrients versus the leca which is completely inert.

I didn't think the bark was providing nutrients, especially since it is not composted. I thought that was a nitrogen drain. I'm still new to this though so I could be completely wrong.

I see that many growers are going to 50% Turface MVP and 50% Miracle Grow Garden Soil.

I was "this" close to trying the Turface/Miracle Grow mix and then I read some disparaging things on Turface yesterday. Maybe I should have gone that route. There's always next time....

Not sure if you can find something similar close to you, but iI stumbled on some pine bark mulch at Lowe’s in Kansas, pictured below.iI have to sieve out about half of the bark because it is too big, but at $4 a bag i had enough to fill a few tubs full for a long while!

I have scoured all the big box and nurseries in my area. The best I can find is a product called Garden Time pathway cover at HD. I can get the timberline product through ACE but it's $20 in shipping alone.

If you have local access to horticultural-grade 3/8" Pumice, that is great stuff as an additive! I know it's all over California. I have to order it here and shipping is nuts. It's heavier than Perlite, but really holds up over time. It doesn't hold too much moisture and provides good aeration. Bonsai enthusiasts use it. It does add to the weight of the pot though.

I would definitely agree that pumice is a great addition to a good soil. I, personally, use soils that contain it in place of the perlite and I love it. As for clay, not necessarily the clay balls for hydroponics, but in bonsai akadama, a type of clay, is often added to soils. It comes in different sizes from tiny to large and there are some enthusiasts that I've heard of that grow their trees in 100% akadama. I would hesitate, however, to use such a medium in a desert environment as it would make it critical to water regularly, which could be a challenge on hot days.