If your looking to breed shrimp then RCS is the way to start. You can do about 8-10ish and as long as you keep stable water and temps in the 70's, they'll readily breed. In a 4 gal
I wouldn't add any other types of shrimp, keep it at RCS personally.
75g Planted Barbs Denison, BlackRuby, Tiger, Albino Tiger, Green Tiger, Cherry, Gold, Checkered, Odessa.
NonBarbs Cardinal, Neon, RummyNose, Bloodfin Tetras, Z. Danios. 1RTS. Amano, Bamboo, Ghost & RCS. 20g Long Shrimp Tank RCS, Tiger, Amano.