All would be very similar to trimming plants in a yard/garden but in miniature.
You can do either with stems. Trim tops and replant or separate. They get leggy in the bottom area where the tops and density of the stems shade them.
When originally planting the stems from the bunch they come in they should be planted separately, individually, for better growth to help allow the light to get down between them. (Kinda like if you had a bunch of onion starts from the store in a bundle and if you just planted them in one hole you wouldn't get good growth and a good harvest.)
As for the other kinds of plants which multiply in place you can see where bunches of growth are, the rosettes of growth, like in the Amazon Sword, each Rosette can be another plant, or at least moved away from the main plant.
Placement in odd number offset patterns...
Had to edit out the pattern because it didn't come out right!
