If you like otos, eight is fine, though I would add these last and maybe a few less (?) but that is up to you. Otos almost always arrive in stores nearly starved, and they need a tank with algae in most cases or they will die quickly. Store tanks rarely provide algae for the otos to eat, and they may or may not immediately take to prepared foods like algae-based tablets. Once they do, the lack of much algae is not a problem. Dried leaves such as oak and beech are ideal for tanks with otos.
Generally it is OK to combine different species of Corydoras, but when it comes to the three "dwarf" species, not so good. I would have C. habrosus or C. trilineatus and a few more of whichever is also OK. Not an issue of incompatibility, just one of the dwarf species being very sensitive and somewhat better off on their own.
BTW, there is technically no "false julii" though I know what you mean. For some reason, the cory labelled C. julii is very often not this species but another, and C. trilineatus is the usual one. I know over on the cory site Ian Fuller objects to the use of "false juli" and I accept that.
There are some other cory confusions in the trade, one of the more common being the cories labelled as C. adolfoi when in fact they are C. duplicareus. Both species do appear as imports but the latter is more common because it is frankly a more attractive fish and more popular as a result. The black dorso-lateral stripe is much wider, and the orange post-orbital fleck is much brighter orange.
