Des... Kuhlis are tropical, not sub-tropical. They certainly are cute, but they're not the right fish for your setup, IMO.
To answer your questions -
1. No. 10 gallons is too small for kuhlis and any loach. I keep mine in a 30, and it's still too small. They wander and set up their own territories. 10 gallons is not big enough.
2. Different species of kuhlis can be kept together, but they tend not to swim as one. Kuhlis represent a wide range of species collected from scattered sites. One is not the other in terms of group dynamic.
3. 22C is down around 72F. This is not sufficient for keeping kuhlis, IMO. It is certainly not ideal. These fish are found in slow moving water - sometimes black water. Again, these are not the right fish to choose.
4. Start at the website of field collector, Antti Vuorela.
http://www.kolumbus.fi/vuorela.antti/indexenglish.htm
His amazing contribution is to show photos of the environments in which some kuhlis are found.
I have a great reverence for loaches, and for kuhlis in particular. They are tough fish, but they should be given an environment that suits their needs, and not the other way round. My rant, my bad.
Your vantage point determines what you can see.