Microsoft recommends you should use Config #2 Legacy MBR Boot mode should not be used. For more information, see this KB article: KB2920188. Microsoft has also backported TPM 2.0 support to Windows 7 for when it is installed in UEFI mode. If firmware defaults to UEFI boot mode leaving Int10 CSM enabled, then Win7 will install successfully in UEFI mode. You can boot Win7 in UEFI mode if a partial CSM is in place (enabled) providing Int10 support.
Windows 7 has a dependency on Int10 support for basic display when the high-res graphics driver is not available (for example, Bugcheck, Sleep transitions, etc.), a dependency satisfied by the CSM. Windows 7 is not able to support Config #1. You will need to enable the CSM and set default to UEFI boot, falling back to legacy boot only if needed. Specifically, for Windows 7 it is recommended to use Config #2.