A quick note, be cautious with plecos. The common ones get HUGE and many of the smaller ones have fairly specific dietary needs. Also, common plecos really only eat algae when they are younger because they are actually omnivores. Bristlenose plecos do best with some drift wood in their diet, and clown plecos need it.
The pitbull pleco, rubberlip pleco, and bristlenose pleco are all smaller plecos that will generally do well in a community setting and eat algae for their whole lives. Typically, they just eat the green algae that grows on your glass. I still suggest a bot of driftwood for any pleco though. Even just a small bit is ok, so they have it if they need it.
Nerite snails will eat the hard algae that gets stuck on ornaments ect. They are the only species I have seen scrape algae off glass once it has gotten stuck on. They have a smaller bioload than the mystery snails, but they also tend to leave little white eggs crusted on the glass, and that can be a bit annoying. They don't actually reproduce in freshwater though, so no excess snails!
Apple snails (including the mystery snail) are not exclusive algae eaters and tend to do a pretty poor job of it. They will eat fallen food and whatnot, but have a significant bioload for their size (as you have now seen firsthand). Also, they will eat algae wafers and sinking pellets and blanched vegetables.
Cories also need some meat in their diet and should be fed sinking food to make sure they get enough to eat. They will certainly eat flakes as well though, and some are better at snatching food up before it falls than others are. they do not eat algae, and need some meaty substance in their diet.
Loaches are similar to cories. Most common loaches (clown, zebra, yo-yo, angelicus) will eat snails. They typically leave alone larger snails though. I have zebra loaches in with nerite snails and they have lived harmoniously for about 2 years. But, smaller snails will be eaten. I breed ramshorns in a different tank and then dump them in with the loaches. They enjoy a variety of food, and make sure they get something that sinks and not just fallen flakes. The kuhli loach is generally considered snail safe because it's mouth is too small for eating most snails. That said, there are stories of them grabbing a snail every once in awhile.
Amano shrimp will eat algae, including hair algae. They will also eat flakes. Mine will come out and steal flakes while they are falling.
Chinese algae eaters only eat algae when young, after that they prefer meatier foods and also get an attitude with many other fish, so be cautious of them. They are very commonly sold as "algae eaters" or "sucker fish" and people end up with more than they bargained for.
Ghost shrimp will eat flakes and whatnot, but are not big into algae. The bioload on shrimp is negligible.
If there is more you need to know, feel free to ask about specifics. It is great to see somebody who doesn't expect the "clean up crew" to actually do all the cleaning.