Force Start - What is it good for?
When you open the context menu of a torrent (by right-clicking) you can choose Queue or Force Start commands, among other choices. Force Start is used for starting a torrent manually. This torrent will be out of order from the queue and will not adhere to the normal queue logic, hopefully set to follow Good settings.
Many newbies think Force Start helps to let them download 10 or even more torrents at once, because they don't like that some torrents are queued.
But Force Start only seems to allow this. Because it overrides your (hopefully) Good settings, using Force Start will spread out your upload capacity over too many upload slots - and your overall download speed will actually suffer.
The Force Start setting is disabled in Beginner Mode. This is because frequent misuse caused confusion among naive users, and too many help requests. Therefore, only users who have set their "User proficiency" in Mode options to Intermediate or Advanced will see Force Start when opening the torrent's context menu.
Read the Azureus FAQ