The results from the cycle look like it is proceeding well.
I have recently got a few pieces of redmoor wood, it is very good for tying java fern to and for looping stems of hornwort round
It took about a week for my pieces to sink and they did exude a sort of clear-whitish goo which my amano shrimp made short work of once it went in the tank. (I should have more amanos but this is the last survivor of a group I bought 5 years ago).
Amanos make a good addition to a tank, preferably a group of them. This species is big enough not to get eaten, though they don't breed in fresh water (the larvae need salt water to develop). Cherry shrimp would be fine too; with the size tank you have you can't fit fish big enough to eat the adults (except a betta) though even small fish will eat baby shrimps.
If you do get shrimps, make sure you have a few hiding places for them. Shrimps have to moult to grow and while the new skin hardens, they are very vulnerable.
According to the manufacturer's website, the Aqua Nano 40 is a 40cm cube. I prefer
Seriously Fish for tank sizes etc for any given species. According to SF:
5 band barbs need a tank with a 80 x 30cm footprint
checkered barbs need 60 x 30
cherry barbs 60 x 30
ember tetra 45 x 30 - these would fit! But they prefer softer water with lower pH.
How hard is your water? Your water company's website should give a number, though it could be in any of half a dozen units. SF reckons ember tetras are OK up to 179ppm, aka 10 german degrees. And hardness is more important than pH.
I have some ember tetras. In the first tank I put them in, they hid all the time and were pale orange. I moved them to another tank and they came out and are deep orange red.
If your water turns out to be very hard, endlers livebearers would be fine in that water and your tank. Just males as they breed like rabbits. A group of males is a very colourful addition to a tank; there are several different colour types if you look at different shops.
Snails are not that bad for an aquarium, provided there aren't so many of them there is no room for anything else
I have some of those tiny flat spiral ones, I gave up trying to get rid of them years ago. Once you have fish, if you don't over feed the snail numbers will stabilise at something manageable. I would just learn to live with them.