You start to have a lot of foliage it ets hard to check every spot after a while so using something like a pipe cleaner is perfect you don't have to actually twist it around the branch just bend it over the branch it will hold perfectly. I only say this because I forgot to untie a branch once and the branch grew and chopped itself off when I pulled it one day. The string cut it as it grew
Leave em. The more foliage you have for as long as you can the plant will use it like food. The natural process is for the plant to use what it needs and then drop the leaf. When you flower you can see all sorts of cool colors you'd never think the plants would turn. Before growing I had no idea that a plant could be bright yellow and purple with green buds. These plants rule. So does growing your own