Backups: Time Machine vs Manual?

I am wondering how you all handle huge backups prior to running OCLP. I already have Time Machine and this is over 1TB worth of files, but I read that if I upgrade my machine with OCLP, use Time Machine to restore files, then *IF* things go south and I have to go back to my original OS, my Time Machine backup can't be used anymore on the old OS. So I am fearful *what if* I have to do a clean reinstall, upgrade, restore from Time Machine, and 2 weeks later I notice it's not a fit and I need to go back... then I'm basically screwed right? I guess the only alternative would be to put some more funds into this project and get a second 2TB external to manually drag all files into?

What are your thoughts in general on using Time Machine to restore files after OCLP? I would love to get rid of all the garbage that is currently on my machine and just drag over the folders I really care about from Time Machine, but I guess that's not an option, either all or nothing? Any thoughts on this topic I'd much appreciate, since my files are so huge it would be nice to just use Time Machine since that is all backed up and set, but obviously I care about speed and don't want to drag old (potentially harmful) things onto my new OS....