To sketch some ideas and get ideas about water changes and whatnot I like to use the site aqadvisor.com it doesn't give compatibility but it helps sketch out how much you can fit in a tank with the current filter and stuff. It's pretty nifty ^^
For shrimp, it depends on what you want it to do. Ghost shrimp are most scavengers and don't eat a lot of algae, they also have claws where most other shrimp don't and can be a bit territorial when with other shrimp so it's kind of a hit or miss.
Cherry shrimp and Amano shrimp are great to get because they act like an assembly line for algae and other small particles. The Amano breaks down bigger things and then the Cherries break down/eat the rest. They also eat different kinds of algae if that's what you're looking for but will also scavenge and eat some fresh left over flakes or whatnot. Also you can pretty much get as many as you want (within reason) because they practically have no bio-load, it's just really small so they won't really effect your ammonia levels or anything.
I don't know much about snails but I know Nerites are one of the best algae cleaners around.
All corydoras are scavengers as well and will eat some algae here a there, you could get a Bristlenose Pleco as those only get to be about 4 inches but they do have a large bio-load. In my 33 I have 6 Dainty/Dwarf Corydoras (Corydoras Habrosus) and 1 BN pleco. It works well because the cories stir up the sand which gets more debris to the filter rather than laying around. They also only get to an inch so you can have more rather than regular cories which normally get to 2 inches to 3 inches depending on variation.
In my 33 I fit 9 girls but could easily be upwards of 15 or so. So in a 29 I would say that 12-13 is fine if you want that many, but you also have to account for other fish (this is where the aqadvisor comes in handy)
Hope that helps a bit, sorry for the long winded post lol
Leopards: 1:4 Hawkeye, Luna, Astrael, Dorian, Cullen