I'm fine with the slow growth, but some plants I want to try are sold/described as med. light plants that don't necessarily require CO2. I am def. worried about going too overkill. Do you have any suggestions on what might be a medium light for my type of tank?
Pretend that light is like a personal trainer at the gym, the plant is you, and co2 is your high calorie meal replacement protein shakes.
If you get the toughest personal trainer who forces you to lift weights for 4 hours a day at the highest intensity (high light), you're going to need a lot of protein shakes (co2) and nutrition (ferts) to build muscle and stay healthy (plant mass).
But let's say they take away your protein shakes (no-co2) and still force you to lift weights 4 hours a day high intensity (high light). You'll still build some muscle for a while (plant mass), but your body is going to have to start eating its fat reserves to keep going (unhealthy older plant growth). If you keep this up too long, you're going to be protein starved (co2 deficient), and you're going to be really unhealthy (dead/dying/weak old plant growth). Plus, some of the other people at the gym who aren't working out as hard (algae) don't need the extra protein shakes, so they are making gains while you suffer.
If you decide to push the limits of what's reasonable, you could try to do a medium intensity workout (medium light) with a 1 protein shake regimen (atmospheric c02), but you're still probably not going to meet your body's needs long term, and you won't be your healthiest. Plus, those other low-intensity people at the gym still have a chance to outperform.
Or you could get a really relaxed personal trainer who only makes you do a few repetitions a day (low light), and you always get to have 1 protein shake afterwards (atmospheric c02). You'll still build muscle mass (plant mass), but it will just take a long time, as long as your goals (types of plants you want to grow) are realistic. Like, if you want to look like Hafţór Júlíus Björnsson (high-light plant), you will NOT get there without using high-light (and co2 and ferts).
So, when plants are "sold/described as med. light plants that don't necessarily require CO2," that's probably not the whole story. Just because they grow better with medium light does not mean that they will grow healthy and stay healthy
long-term without c02 under medium light.
This page is probably a good reasonable reference (and actually links back to an old Planted Tank forum thread):