There is no problem with doing both. Some varieties are more likely to be stressed than others, but in general most can handle a good haircut or tyeing down, or both. I've spent years trying to figure out which yields the most. I have yet to come up with a conclusion other than this:
They yield about the same.
If you top or FIM, you get more main colas. If you LST you get more secondary colas. If you do nothing, you get even less colas. Whatever you do, it will yield roughly the same if you don't consider any setback from possible stress. I've grown less than 10 varieties to completion so far, but all of them don't seem to mind a little damage. Luckily for us weed is a weed.
How you decide to prune should not depend on what other people do, but what works best for your situation. I wouldn't consider an outdoor grow without at least one round of topping or FIMing. If you can keep your outdoor plants bushy and low they will be less likely to be seen and less likely to break or fall over in the wind, or just from bud weight. If my main goal was donkey dick bud pictures, I would remove everything except maybe 3 or 4 of the healthiest colas, or maybe even do a lollipop grow. If my main goal was spreading the canopy out under a square screen I would do a combination of topping or FIM, and LST. If my main goal was keeping the plant low I might try LST only.
It's been my experience that however you decide to prune, your yield will be roughly the same. IMO having many smaller buds is a huge disadvantage when it comes time to manicure them. If you have a decent yield your hands will soon tire and your brain will soon turn to mush if you didn't already make it do that before picking up the scissors.
