Khulis won't pester your other fish, and they can be very entertaining. Kept in a large group, they are very active. They do eat small snails, I found this out when I noticed a sharp decline in the ramshorn population in my sister's community tank, and then noticed the khuli loaches scavenging baby snail shells.
Horsefaced loaches do like to bury themselves in the substrate, with only their nose sticking out. From what I remember, they also like to be kept in groups.
Personally, I'd avoid the bichir with your other fish. I just wouldn't trust one once it got to about 6 inches, and they can grow fast. They are voracious and very adept predators. (I have 2 Sengal bichirs in a 180g.)