I live in Melbourne, and we have pretty soft water here, with about 7 pH still. So, I actually don't use an active substrate. I use AquaIron by Oliver Knott and Pisces in my main tank, bare bottom in 3 of my 5 gallons (inert substrate in a tub in one), and an inert substrate in my last 5 gallon (Sorry if I switch between metric and imperial - I naturally use metric, but I've learnt to use imperial since most of the fish keeping community online uses it).
My pH in the main tank, with all that in mind, is about 5-5.5... Now, that is 100% from the driftwood. It's a random piece of driftwood I collected at the beach, looks fantastic, and is kinda massive.
My pH in the other tanks tends to be around 6.5-7, since I use crushed coral to raise it up a little (I keep and breed blue dreams - neocaridinas - and tangerine tiger shrimp, which can do well in a slightly lower range than neos.
Uhm, I have caridinas and don't use RO, so I wouldn't say that investment is necessary. If you want to try Taiwan Bees, @sdlTBfanUK can help you more than I can. I would give it a year or so before transitioning into them though. You could probably do crystals and tigers with an active substrate and some wood, without RO.
I cannot recommend this enough. TDS isn't necessary with neos, but it would be great for the survival and well-being of your shrimp if you could test the water, say with the API kits - Ammonia, nitrite, nitrate, pH, GH & KH.
Sorry to hear that! If it was 3/8, there might be something going on with your water. I find my shrimp become way more active (constant grazing, flying around the tank) when the water is just right.
Could I ask what you're doing in terms of food?