I would say root, then get the pay version of rom manager and from there its easy to flash whatever you want without constanly booting in recovery.
the new ultimate droid extreme 350 is by far the fastest i have saw yet and heres the proof for ya as you can see the new stock theme is consisted of like five different themes thrown together. The best of each one.......insanenemesis i think did the main part of the theme.. i dunno?
you know the speed of a rom is all in the kernel...pick your fave rom...and flash kernels for the speed you want!!
also cut down on your widgets they eat resources...if yuh fast thinks fast...less is more...jakes kernels are always fastest out ....on quad i hit 18-20 fps..on a p3 kernel....with a jakes kernel it will run upwards of 28-30 fps...thats a big diffrence...
so to sum it up....pick your fav rom....flash a faster kernel!!!
ok then ......ultimate droid extreme 350 has the most customizable rom out to date....you do not need any apps to make scripts work its all built in already!!! all you do is go to ultimatedroid customizations settings and there you go. you can install and uninstall on the fly to...and colors you can change any part of the framework you want..im sure i am leaving something else out?