Yes, you need root to uninstall bloatware.
I think Root uninstaller is a specific for another phone type (i.e. doesn't work with xperia play (or atleast the full version doesn't) .
I've used both Titanium Backup and My Backup Pro, and I like titanium backup better.
Root explorer is for people who feel comfortable maneuvering around linux file structure, I'd suggest staying away from using that, unless you have previous experience with linux (or just wanna learn)