If you are going to fill your tank with plants, then it would probably be better to break up and disperse the root tabs, and keep them as close to the bottom as possible so it doesn't all leach out into the water column right away.
If you are only having a couple plants/clusters, then it would be better to use fewer near the plants.
For a low-tech, I wouldn't worry quite as much about dosing the water column, the fish will probably take care of this for you.
I've found it easier to plant things when the tank is empty (or nearly so), and then fill.
Java fern and Anubias are great. pretty tolerant plants, and I like how they eventually just cling to the wood/rocks.