9.1 is not "very different" from 8.6 except that it eats a lot more ram and has a "keychain" for various passwords. I've never used that software. It also crashes more. 9.2 is really only interesting for people who are running X. It is an update so the interface between "classic" and X runs more smoothly. If you aren't going to be running X, then you don't need to upgrade to 9.2.

In fact, 8.6 was the most stable Mac OS. If you have an older Mac and have no other reason for upgrading, you should stick with 8.6. If you have less that 350 MHz to play with, you will also take a speed hit with 9, though not dramatic.

To change locations for the sharing folder, go to tools>options>sharing.

Actually, Limewire is a rather small program. What you are seeing devouring your computer resources is Java. Think of it as running a really lousy version of VirtualPC in order to run Limewire.

I still am not sure we are talking about the same thing. To upgrade to 9.1, all you have to do is stick in the CD, tell it which volume, and install the software. You don't have to prepare in any other way except the customary backup of files you can't replace. A "clean install" usually refers to installing the same version of the sys software in order to alleviate various problems. There is an option to create an entirely new system folder upon installation. This is a "clean install", because there are not yet any third party extensions, etc. in the sys folder. What you are planning sounds to me like simply upgrading your sys software. The installer does this automatically. There are also no strange holdovers as there was when you upgraded from 8 to 8.5.

Changing the location of an app is not going to change the way it behaves, except with certain video editing software, where it is helpful to have various files on different drives. LW will still eat the same amount of computer power regardless of where you put it -- besides the trash, that is!