Hello Lane,
1) Yes you can use both without conflicts - presuming you install PowerTools in a separate folder. Uninstalling "PT 2006", after the trial period, should not create problems.
2) There is not such a feature in RegSupreme Pro. An available update should be installed over the previous version, as so you keep your settings and Backups. If you want to do a clean install you have do do a Backup of the the Data and Backup folders.
P.s.: For RegSupreme Pro user there is also a special upgrade price, see
http://www.macecraft.com/pricelist/
If you are using an Win9x system, you will find, since 27.10, an updated version of "PT".
Jean-Paul