I’ve thought that Windows Photo Viewer is a nicely optimized and lightweight program to preview photos. As it has been disabled by default on certain versions of Windows 10, this quick cmdlet should bring it back in a jiffy:

Get-AppxPackage -allusers Microsoft.Windows.Photos | Foreach {Add-AppxPackage -DisableDevelopmentMode -Register "$($_.InstallLocation)\AppXManifest.xml"}