I would always test Nitrates in combination with Phosphate and decide next steps based on the combined results.
Water changes are an effective way to reduce nitrate (and phosphate) - and reduced feeding.
Carbon dosing for combined nitrate and phosphate reductions is my preference as the other methods have side effects - except zeolithe.
For carbon dosing I would use ElimiNP from Tropic marin as this can be dialed in best.
Edit: Nitrates above 20 mg/l require treatment from my perspective. My target is below 10 mg/l.
I know next to nothing about carbon dosing, so it's not something I would be confident in or even consider trying in a tank with my precious fish unless I actually knew what I was doing. I have watched a few random videos about it yet they didn't make me any more informed. All the different videos had different methods and different suggestions than the others ones leaving me even more confused as to who to actually listen to. So I never gave it any serious consideration.
At some point, I may try it if I ever get to a level of understanding that would let me be confident in trying it on one of my tanks.