It’s always worth checking Tropica’s website (go into all the drop down menus for various plant, fertilizers, substrate, etc information), on their YouTube channel they offer a
Plant Handling Playlist
This video from Juries mit JS is more about longterm stem maintenance
A Green Aqua trimming video - this method always leaves the tank looking fantastic
Wherever you trim plants, 2 new shoots will generate quite quickly IF plant is healthy and there are sufficient light and nutrients etc (so in a nonCO2 aquarium this regrowth can be much slower and always replanting the tops (all or some) is more effective) - obviously “fast” growing plants will fill back in much more quickly than “slow” growing plant
(again Tropica website includes this sort of information on their plants)
Choose the first cut quite low, you want progressive cuts to be higher so that plant “bushes”
If there is sufficient hardscape etc, then choose your first cuts so it is hidden behind
Replanting tops into the same area will obviously help fill in plants quicker BUT depending on your light (and flow), doing this can impede new shoot development (it won’t prevent it but new shoots may be weak or have long internode distance as they “leap” toward the light)
Obviously plants that are established with good root systems and thicker stems, will rebound much more quickly and robustly, hence the (often) recommendation to begin trimming after a few weeks, allowing significant growth first
Eventually as the upper plant becomes very full, minimal light and leaf age, will lead to basically bare stems at the base of most (stem) plants - at this point, trim as shown in the videos and replant
You can dig out some of the old roots etc (running syphon to remove the debris cloud - also add 5-10X Prime to bind any ammonia (& nitrites) released) - my preference
Sorry for the late reply, different time zones means you’ve likely already finished your plant adventure