It's generally safe to delete them. The worst that could happen when deleting the majority of them is that you lose settings associated with the program that uses that plist. The bad ones are generally locked out by SIP in 10.11 and later, but even then it's generally safe to delete those as well.
Yes.... the next time you open the setting or app related to that plist, it will create a new one with the default settings.
Also, just deleting a plist will not get rid of it starting with Mavericks. The plist files are cached, so if you just delete one the cached version will be used and you will have accomplished nothing. So you need to quit the app, delete the plist file, logout then log back in or reboot to erase the cached plist, then start the app the generate a new plist.