In most situations there will be no problem installing in Safe Mode, and in
fact there should be less likelihood of problems than if doing it in Normal
Mode. Though usually there are no problems either way.

If an installation uses DOS applications and/or requires the detection of a
USB device, it may not succeed in Safe Mode. Quite possibly installation
would complete successfully on rebooting to Normal Mode, however.

Chipset and Graphics driver installations are more likely to succeed in Safe
Mode if they freeze when trying to install them in Normal Mode.

By and large, the clue is in the name.

Shane