Once I started mainlining indoors, I never went back. You don't need to do it, you can just leave all the branches and start topping and training and get a nice canopy that way, but look into mainlining if you aren't really sure how or when to start topping-there are plenty of pictorial guides online to get you started.
As far as defoliation, just keep in mind you are removing leaves that could save your plant in the event something goes wrong-like nutrient lockout, AC giving out, etc. I like to trim underneath the canopy a bit, just to open it up for the fan I keep down there, but I don't remove any fan leaves that are receiving direct light. Defoliation can induce systemic resistance by simulating an herbivore or pathogen attacking the plant-it doesn't require the removing of the majority of leaves to do this-but most people don't defoliate for that reason, or for increasing air circulation. Most do it because they read that fan leaves "drain the plant of energy" or some other such nonsense. Imagine a solar farm....now imagine someone removing solar panels because they are "draining the farm of energy." Does that make sense? Fan leaves store nutrients for the plant to use at will-like a prepper with a shed full of baked beans-don't leave your plant unprepared!
Anyway, check out mainlining as a training technique-it results in very nice uniform buds, whether you top for 8 colas or 32+. The more bud sites you leave, the smaller the resulting buds will be, but you'll get maximum yield out of a given space by filling it up with colas. Good luck!