One thing you could try, if you can find any - leopard danios are the same species as zebra danios so they would consider themselves as part of the same shoal. This would increase the visual variety while still having a big enough shoal. Perhaps get 4 zebras and 4 leopards?
And I've seen albino cherry barbs as my local branch of Maidenhead Aquatics, if there is one near you. They could be mixed with red cherry barbs as they are the same species.
Going over 100% in the community creator means you will have to keep on top of your water changes. If you do that, there should be no problem.
If you have an undergravel filter live plants are not recommended as the water flow through the gravel disturbs the roots. I had fake plants for years, I've only recently got into live ones. If you want to try live plants later, the best choice would be java fern or anubias (several species) because they are grown attached to decor rather than planted in the gravel. And they are fine with undergravels. And don't need strong light.
Re the pH, it depends on how hard your water is. There are two types of hardness.
General hardness, or GH, is what causes limescale in the kettle or showerhead. This is what websites mean when they say this fish needs soft water or that fish needs hard water. You can usually find the hardness of your tapwater somewhere on your water company's website.
The other hardness is carbonate hardness, or KH. Usually, if GH is high, so is KH and vice versa. KH doesn't affect the fish directly, unlike GH, but it does affect pH. Carbonate reatcs with acids to keep the pH stable. If there is a lot of carbonate in the water it is very difficult to change the pH, while with low carbonate it is easy to change the pH.
The first thing to do is look at your water company's website to see if you have hard, soft or middling water. If it is hard, adding wood probably won't have much impact on your pH.
But zebra danios are fine up to pH 8 and hard water, as are cherry barbs.