I would stay away from the lag fix... Causes more problems than it fixes, and doesn't really do much to fix any lag that most people don't even notice in the first place.
Edit: I actually noticed a pretty good increase in battery life after uninstalling the lag fix app.
For the rest of your questions, I would start by downloading Root Explorer from the market (a purchase that is worth it). With Root Explorer you can go into the /system/app folder and begin removing bloat. One of the safer ways to do this is simply renaming the apps you want to get rid of. You can do this by long-pressing the file (ending in .apk) and adding a ".old" to the end (so it reads "filename.apk.old"). Another way to remove the files is by moving them to your SD card for safe keeping. Keep in mind that OTA updates usually check for certain files on the phone in order for them to push through correctly, so I wouldn't go through and delete everything.
In order to get Google fully functional, download the .apk from the sticky "Got it! Google widget works now. Bing is dead!" to your mac and move it to your SD card. Using the My Files app (native to the phone, preinstalled) locate the file (enhancedgooglesearchprovider.apk) and click on it. It should prompt you to install the app. This will enable to you to use the search button to perform Google searches. If you want to use the Google widget, you will have to install a third party launcher like LauncherPro.
Anything else you would like to do?