What I do remember is, the bucket or container, must have a good seal and the cover/lid's clamps, should be able to withstand the water pressure. Some folks went with those Lock n Lock containers, but the lid's clamps were not strong enough to withstand the pressure.
I have no idea how powerful the pump should be, but making it "silent" should be easy if you used foam around the whole thing. I doubt you can effectively make the DIY canister totally silent, if there is trapped air within the container.
The most silent canister I've used to date is still an Eden 501, but it will be insufficient with an Oscar and a Pleco in the same tank. I am fairly certain your Penguin HOBs should be sufficient, if you keep to regular water changes and don't overfeed the Oscar and Pleco.
Rather than DIY a canister of your own, you might want to consider doing a wet/dry sump filter instead.
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