Since I hope to make this work without CO2 (initially, at least), I know it's going to be important to maximize filtration (lots of fish - worried about algae) while minimizing surface agitation. This is especially true because wpg=2.66.
While I don't want to discourage you, things aren't sounding too good at the moment! You mentioned 2.66 wpg, a high fish load, and NO CO2. That recipe generally bakes disaster! Hoping to get by until later with CO2 is normally an effort in futility since with that type of setup CO2 will be MOST IMPORTANT in the beginning. Algae generally make a good attempt at getting a foothold in the tank until it gets VERY established. 5 top of the line filters won't stop algae! Your light almost requires CO2, especially in a more shallow tank (18" or less). Your high fish load (right in the beginning) is going to be the most difficult task to overcome, even with CO2 running full throttle. Trust me, if you are going to start a planted tank, it's much nicer to be patient in the beginning and make sure you have a good chance of success. Trying to deal with massive algae problems will widdle-away at your patience, enjoyment, and time!
DIY (two liter bottles) CO2 is VERY easy to make, although it may seem difficult if you've never done it before. You will have better odds with AT LEAST using that! I did DIY CO2 for almost 1 year, and went to pressurized when I upgraded to a 55 gallon (from a 20 gallon). If you can, though, probably the best thing you can do is to slow down and add fish slowly to your setup. Let things mature, and get established before it has to deal with that much of a fish load. It's not just the nitrate produced, but when you feed that many fish, you tend to add much more phosphate as well. It's also more to worry about with all those fish running around. The plants will keep your hands full enough for a while, till you get the hang of the tank. Even if you've had planted tanks before, each tank is different, and you have to figure out exactly how this one responds. Best of wishes.
"For the Son of Man came to seek and to save what was lost"
Luke 19:10 NIV