Plugin questions/problems.

CalypsoArt

How to remove a Plugin? (Not just disable in Plugin manager) Will just deleting it from the plugin folder cause any problems?
How to remove superfluous plugin folder?

Every time I Autoinstall a plugin through the Plugin store it gives me the message

"You can Write to the Main Plugins Folder, and...You have a Custom-Plugins Folder."
and asks to chooses the folder. Below are the two options. The top being the main plugin folder.

C:\Users\Nicholas\AppData\Roaming\SketchUp\SketchUp 2014\SketchUp\Plugins
C:\ProgramData\SketchUp\SketchUp 2014\SketchUp\Plugins

I've checked and I only have 3 plugins in the second folder. If I reinstall those into the main folder, can I just delete it?

The "Shapes" plugin will not install correctly.

The folder thing came to light trying to install the @Last Shapes plugin. (I want the ability to create quickly Domes and Toruses.) However, in one folder it won't install, and when installed in the other it causes an error and will not load. I'd like to clean all this up and only have one place for plugins.

Box

Some plugins are helper files used by others so you need to be a bit aware of what you are actually removing.
If you use the uninstall feature of Sketchucation tools it renames the files to .rbx therefore disabling them. Like most things computer related it helps to keep things around until you are sure they aren't needed. You'll know at the next startup if anything really obvious needs to be reinstalled, but there may be other error that won't show until you actually try to use a plugin that needs a specific helper file. Eventually you could remove all .rbx files if you really need the space.
Tig could give you much more info on this.

I'd guess the other plugin folder has been created by a Renderer or some such plugin that installs from an exe file.
What are the plugins in it?
Easiest way to check if you can move the file to your main one is,
Copy the files to the main plugins and rename the superfluous folder so it won't be recognised. Open SU and see if the three plugins function, if they do problem solved.

The @Last Shapes plugin is very old and doesn't work with 2014, there is a second newer version available in the Pluginstore and the Extension warehouse.
http://sketchucation.com/pluginstore?pln=jwm_shapes