As this is your first planted tank, I’d suggest taking the simplest route
- tap water: so you can quickly perform water changes whenever needed, and as often as dictated by unusual circumstances, eg, algae outbreak, fish illness etc
- select livestock that will manage in your tap water (you likely can select domestic bred SA stock that will manage fine for some time, then gradually transition tank to an RO/tap mix)
- if going the tap route, deal with a shop that keeps planted tank in this manner (Scaped Nature, Aquarium Gardens obviously come to mind) and follow their recommendations for plant species
- add CO2 as this will definitely assist plants with hard water challenge (as you may guess I don’t agree that CO2 is a challenge for a beginning plant keeper - it makes such a difference in plant health, ease of transition etc - adding CO2 doesn’t mean you must also go high light, high nutrients, rapid plant growth etc ... follow the methodology where nutrients are enriched in the substrate with lean water column dosing)
Of course, if you go the RO route, it may be that you only ever have minimal algae issues, and you immediately (relatively) have the fish and style of tank you want (make sure to have sufficient water stored on hand for a 90% water change as this will mean that you can do a couple 50% water changes without needing to wait on RO production, you’ll also be prepared in case of any slowdowns with the RO system)
Frequent water changes, dealing with algae as soon as it appears (establish a varied algae crew from the start as they will always find algae before it’s obvious to the human eye), starting the tank with sufficient plants (and including some “auxiliary plants”
Auxiliary plants - supporting plants for the aquarium - Tropica Aquarium Plants ), 6-8 hour maximum photoperiod (also consider ambient light effects if you’re choosing an evening photoperiod for viewing preferences) etc
I strongly suggest reading every page of Tropica’s website, as there is very good, succinct information there