Once the tank is stable, about once a month clean of the mechanical stuff is needed.
You can run a tank off a canister....I did for a decade. but i always Under stocked and over filtered.
Just watch your chems, clean it out when you do water changes.
The Biggest difference between sump vs canister. the largest canisters holds what maybe 5 gals when packed with stuffs?
It's a STOCK BIO load issue IMO(cause sumps can be bio nitrate traps too, and crap people talk about tossing socks out like they are paper towels). You can stock a tank with more critters if you have 50% more tank/water volume under it. vs same tank and a 5th of the water volume is going to cause problems. SW filtration while chemical and mechanical filtration its part of it... BIO does the largest part....more water more Bio more breathing room even if the fish can swim into it.