Angelfish are shoaling fish, living in groups in their habitat, so a group of 5+ is recommended. However, you could have some issues with your existing fish. Neons are often viewed as "food" by angels, once they are large enough. Also, neons have been known to nip at the fins of the sedate angels. Bloodfins also have a reputation for fin nipping at times, and angels would undoubtedly be quite a temptation.
The angels might regard the rainbowfish as rivals; perhaps someone here may have experience in this area to help you.
Within the existing fish community, are there any problems with the red tail shark versus the loaches? I have read several recommendations that sharks can be aggressive with such similar fish. While this may not be occurring yet, the possibility is always present.