Well RadeonTweaker, Rage3d Tweaker, and Raid-on all basically do the same thing. I just prefer RadeonTweaker. Ya know it tells what all the settings do in RadeonTweaker and whether he recommends if they are enabled or disabled.
As far as tweaks slowing them down, yes that's possible. I've seen several posts at Rage3d and some people say to not mess with any tweaks as much of the time they can slow things down or cause visual errors. I only use a few tweaks like t&l enabled, vsync enabled, texture compression on, just simple things like that.
I wouldn't flash your LE. All you need to do is get a tweaker, overclock it to 166/166 (that's a safe setting w/o a fan), and enabled hyper-z. There is a option in RadeonTweaker called 'make sure hyper-z is enabled at boot' and it says for that one to be checked if you got a LE.
edit: I noticed in RadeonTweaker, you just goto Options -> Enable Hyper-z on Radeon LE. Then bump up the clock to 166/166 and you're done. Very simple and fast.