Puffers are tricky. They will most likley eat your shrimp, or at least pester them to death. Depending on the tetras you chose it could go either way. Tetras are over all pretty aggressive and may pick at and or harass the puffers. If you want pea puffers I'd set up a nice planted tank like your 29 or 50 easy plants like anubias, crypts, java ferns, and drift wood. Seed it with pond snails or ramshorn snails and let the plants grow in and feed the snails so the populate. Then depending on which tank add 6- 10 pea puffers. Try to get more females then males. Like 1 male rest female. Males get a brown stripe on their bellies when mature and are not as round as females. Once the tank establishes you could add some gammarus shrimp a common detrivoir if enough hidding places they will breed and provide a food source for your puffers. So will the snails.I like my 29 gallon setup it has branches and some fake plants, but I was looking about getting a self filtering tank with shrimp and a pea puffer and maybe some kind of tetras
honestly if just breeding shrimp even 100+ in a 29G wont seem like that many due to their size and nature to hide...I just don’t wanna have to worry about like 100s of shrimp crowding the tank