In many cases the type flow (not necessarily filtration) needed for an aquarium will be determined by the type fish kept, fish are not all the same.
If you want to keep certain bettas, anabantoids, ( swamp dwellers) maybe even discus (oxbows), a low flow situation (especially if you start with young fish) may be adequate
If however you want to keep normal riverine species (large tetras, cichlids, large riveting barbs) that come from areas where water movement is strong your filter (or its pump strength) may not be enough to sustain health.
If you were to keep rheophillic species like tiger fish, Tomocichla tuba, or other species that come from highly oxygenated water in counter current zones or riffles, you filtration will be paltry and even in the span of a year lead to health problems, and aggression. In that case , or even if you want normal riverine species you may want to add a powerhead to supply much more water movement, eliminate dead spots, and add oxygenation.