To make files automatically show thumbnails, you have to change a setting in the Control Panel. The easiest way to get to the control panel is simply to type Control Panel in the search bar on the start menu. Once there, click on Appearance and Personalization.
Then, click on Folder options.
Under folder options, click the View tab at the top.
Finally, make sure to uncheck the square that says “Always show icons, never thumbnails” and you should see the thumbnails when you load up all your folders.
For the second part of the question, if I’m understanding you correctly, you would like to keep your windows the same size. When you close a window, the next window will open to that size. However, it does follow the last window you close. So if you have a small window, and a window that is maximized, if you close the small window first, then the maximized window, the next window you open would be maximized. Likewise, if you close the maximized window first, then the smaller window, your windows will be the size of the small window next time you open one.
~ Sai Kiran
