Bettas are not community fish. And neons have teeth. Long fins and teeth are not a good combination.
You will read of bettas being kept in community tanks, it can work with some individuals. But it is also common for bettas appearing to live peacefully until one day he snaps and goes on a killing spree. Or the tank mates mature and eat the betta's fins. If trying this, always have a back up plan in place right at the beginning in case it goes wrong.
A small school of neons - just how small? They are shoaling fish which need to to be in a group of at least 6 with more being better. Same for the kuhlis.
To go back to the beginning, the first thing you need to know is the hardness of your tap water. You may be able to find this on your water provider's website, though other Irish members have had trouble finding it. Alternatively, take some tap water to a fish store (if there are any open at the moment) and ask them to test for GH. With both the water provider and fish store you need a number and the unit of measurement rather than vague words.
The reason we need the hardness is because there are hard water fish, soft water fish, and a few that need 'middling' water. Soft water fish kept in hard water, and vice versa, with suffer health problems and not live as long as they should. We should aim to keep fish with our tap water hardness around the middle of a fish's preferred range.
All the fish mentioned so far are soft water fish. If your water is hard, none of them would be happy.
If your water supplier is UISCE, use this page
https://www.water.ie/water-supply/water-quality/water-hardness/