A few questions I have before I root my phone

I am planning on rooting my motorola droid to froyo using the v0.4 bugless beast rom (I assume thats the latest version?) But I have a few questions about rooting in general first.

1. Can I save my official 2.1 ROM + all my data using nandroid or something incase I do not like having a rooted phone? also if i do revert back to this will i be able to get OTA updates again?

2. When you are setting up a rom on your phone and it asks what frequency you want your processor running at (600 mhz, 800 mhz, 1 ghz ect.) cant you just pick any of them and download a overclocking/underclocking app and pick whatever clock speed you want?

3. Are there any benefits waiting for the OTA official 2.2 release and THEN rooting my phone? will the roms be better with an official version to work with?