First of all, disregard what I said about it messing up everything in E7 since that only applies when you open, export, and re-import the TGID List.
Okay, now on to the rest of your inquiries. For anything you want to edit quickly, the .csv route is the most efficient way by far because PPS kinda sucks if there's a lot of info. The first step is to export the site list to somewhere easy to find (like the desktop). If Open Office is the default program, just double click the file. The popup should look like this:
View attachment 174925
When it opens, it should look like below. To quickly delete sites, hold down Cntrl as you click the numbers on the far left to highlight entire row. Once you have them selected, right click on one of highlighted rows, and then select "Delete Rows". Close the program, and click to save the changes when you get the popup.
View attachment 174929
When all of that is done, go back to tab E2, click system detail, click on the site list, check the box to delete old data, and import the edited file.
As far as doing the same for the control frequencies, it isn't necessary to remove any of them since it is just a pick-list. The only thing that really matters is if there is at least one that is correct.