I have an FX5 in a 540 ltr tank with plecs,tetras and Cichlids.
They produce lots of waste and I reckon need the filtration.
Otherwise I'd go for the two cannister idea, especially with fish that produce less waste. I have two external in another 4ft and alternate cleaning them, and as it a malawi tank, so low on waste output, the water is never a worry.
UV filter- as others have said, if the tank is in a light room or prone to algae then perhaps otherwise try without.