If I can budget in a CO2 system I personally always go that route. No matter the size of the aquarium. In my opinion there is no replacement for pressurized CO2 injection.
Now with that said some “low tech” plants you can definitely get away with not having to run a CO2 system. As sometimes there is enough in the tap water to keep them going. But going this route you want to keep some times in mind such as more frequent water changes to keep everything replenished properly. Also you want to be careful using air pumps or having too much surface agitation as both of those will get rid of any CO2 in the water fairly quickly. Some excel with this method won’t hurt either.