It's best to be patient in this hobby else you will end up not really enjoying things. Nature needs time to adjust. 3 weeks is literally nothing in the this realm. My amano breeding tank literally took 3 months to cycle and it's still not 100% mature. Use this time to evaluate how your tank evolves and to try to understand the underlying mechanisms.I am struggling to be patient! But it's also only been 3 weeks and the aquarium store said 4-6 weeks for the tank to be ready when using Tropica Soil.
To kill a plant it take some effort and you can always replant some smaller shoots if bigger ones die.
You could add some floating plants to aid in the process.