The only mod that gives you the ability to move individual buttons is flexbar. To be honest i don't know why you would want 120 buttons in random places. I would think that you have your buttons in some sort of line or shape.
I would reccommend looking into Trinity Bars (
http://www.wowinterface.com/download...ity_Bars.html). This gives you 10 "bars" of buttons that can range from 1 to 14 buttons on each bar. You can change their orientation (move them horizontal, vertical, put them in a circle, or put them in arcs). You can change the buttons from squares to circles. You can hide certain bars of buttons, you can change their size and spacing (read the documentation for how to do that).
Your other option is to use FlexBar2, which is in developement at
http://www.wowace.com/files/FlexBar2/ . Please note that this version does NOT contain any slash commands, so you cannot group anything, you cannot show or hide, etc. You can move each individual button. This is an early beta and only has some functionality.
Actually, now that I think of it someone else wrote an addon to give you basic /flexbar commands (such as show/hide/group). It's not official but with Flexbar2 and the slash addon you should be able to get basic functionality. It can be found at:
http://ui.worldofwar.net/ui.php?id=3558
In reguards to your FPS issue. Some of the low FPS is caused just because WoW lags enough server side to cause your FPS to go down. Some of it has to do with the fact that it's a MMORG and it has to draw a million players around Orgimarr or whatever.
Flexbar2 is being re-written as an Ace2 addon. Ace2 addons provide very good performance as they use optimized libraries. If there's any low FPS after Flexbar2 then it's something else and not Flexbar.
I hope this helps.