Don't overstock and do 50% water changes weekly if you want to clear up your water. Also doing weekly cleanup is important. Your filters seem weak, so an upgrade would help. Perhaps substrate is your issue? There could be many problems with your tank if it can't have clear water in its current condition.
IME it was a lot easier and convenient doing water changes compared to setting up a sump since its better for all tank inhabitants (both plants and fish) by replenishing a lot of micronutrients, and you physically remove the waste instead of prolonging water changes to let the wastes rot. SW
people would rather prolong water changes ($alt) with skimmer and growing macroalgae. Most of the micronutrients are replenished when doing small water change since the salt mix is usually packed with lots of micronutrients. The reason why you see saltwater tanks with clear water is because they keep up with good weekly maintenance since more work is needed with those tanks. There are also a lot of tanks that do not have sumps that also have very clear water due to good upkeep. Good upkeep is key
Any freshwater system without CO2
injections would be beneficial (if setup properly) with a sump/refugium, but its not worth the time over complicating things and using more money. If you like tinkering around with your tank, then go ahead and add a sump/refugium. Its more work IME for upkeep.
its considered a refugium when you are growing plants to export nutrients, but it does not matter if you call it a refugium or a sump. You are better off not using bioballs so that you can have more space for plants.
, post if you want clarifications.