Primarily, I used the "I don't know what the hell I'm doing" method.
Ie, my tank was filtered. I maintained good water by testing and frequent water changes, changing 50% of the water 2x per week (I do 2x 30% now), with weekly gravel vac. I also used Stability for the first three weeks not to cycle the tank, it can't do that no matter what the claim is, wrong bacteria - but it does stabilise it a bit while its cycling
The tank eventually cycled with the betta in the tank.
No harm to the fish. But I do think the heavy planting makes a difference to whether the various param spikes are severe enough to cause harm. Also, I tend to overdose lightly with Prime at each water change (you can safely double the dose).
My fish is the best barometer of all when it comes to that. She is always full-finned and happy looking - the moment there's the tiniest amount of ammonia or something not quite right in the tank, she clamps and is visibly unhappy about it. Some fish are less finicky.. I'm glad mine is fussy, it's helped me to catch any problems right away - we had one small crash with an ammonia spike a while back but that was dealt with immediately, and none since.