This site is just a good as monsterfishkeepers on info for freshwater. That link won't do him much justice imo. The question of the sump has been answered. Any method that will work for salt water will work for planted. No matter how you look at it, both drain water from a display to a tank below. The thing is choosing a method that works best for your setup. CO2 or no CO2 is the answer. The goal here is to limit the loss. Since you won't be planting the 180 (sorry to hear your not) then you can careless on your sump being open or sealed to limit CO2 loss or having water splash from the inlet unless you want silence.
For freshwater tanks planted or not, it doesn't require the high circulation that saltwater tanks needs. Planted obviously would need a bit more than non planted to distribute nutrients thru the water column but still not the volume of marine. Freshwater fish typically aren't native to the type of currents of marine. I have seen most stay within the 3x-10x gallons per hour.
Make sure your stock list are all compatible. From water parameters, to food chain and to aggressiveness.