Yes, F12 (Steam default) will capture the actual screen, including whatever UI/glyph sequence is visible, while the ‘left mouse button’ (in-game default PC) will not show UI or glyph overlay. You can however use ‘Left Shift’ to hide UI and glyphs to then take a clean screencap with F12.
The cutting off, from what I understood, is caused by the FOV settings used and taking pictures using the in-game ‘left mouse button’, while F12 actually captures the screen without any cropping.
See more discussion about it here and some of the replies that follow:
And a topic about the issue here:
There have been some fixes regarding this issue, but cropping may still be present?