No not through Google+, you would just need to set up Google Drive. If you already have a Google account (Gmail) you already have the free space allotted on Google Drive. All you need to do is go into your Gallery, select what you want to move to Google Drive, hit the share button and select Google Drive. When you access Google Drive you can create folders and move your files around as needed. When moving your images you probably will want to do it while on wifi to avoid using a lot of your plan data. Once they're on Google Drive you can view and share them just as though they were stored locally on your phone through the Google Drive app as long as you have an Internet connection either through wifi or cellular data.
The other method of backing up your images on Google+ also stores them in your Google Drive space but does not show them through the Google Drive app. Instead you use the Photos app to view them. That is just a shortcut to the Photos section in Google+. Under these circumstances, you have the option of uploading at full resolution or a reduced resolution of 2048 x 2048. If you choose the reduced resolution you have unlimited storage of images. Whereas if you choose the full resolution, anything over 2048 x 2048 counts against your available Google Drive space. I don't find this method as user friendly for my needs, I prefer just using Google Drive but the process of backing up photos to Google Drive is a manual process, while using Google+ for this purpose can be set to backup automatically.
Hope this helps.