Main points to look for:
- Over- and Underexposure display has been improved and refined (Manual, p.132)
• Detecting clipping point for overexposure zones display depending on camera's Make and Model (not available for all cameras)
• Adjusting underexposure limit detection based on camera ISO setting
- Improved synchronization of XMP changes between ACR/Lr and FRV (see "XMP settings" in Manual, p.117)
- Touchscreen support (Manual, pp.68, 126)
- Option to verify data after file copy (Manual, p.36)
- The sorting and filtration of files in folders has been massively overhauled;
• File sorting and filtering (Manual, pp.42, 165):
• by Filename (naturally or alphanumerically)
• by File type (extension)
• by File modification time
• by File size
• by Shooting date (EXIF Timestamp)
• by XMP rating
• Save, Cancel and Restore filters (Manual, p.44)
- Folder tree editing (Manual, p.58)
• Create subfolder
• Rename folder
• Delete folder
- Drag-drop into the folder tree (including Favorite folders) (Manual, pp.50, 112):
• Copy or Move modes
- Drag-drop files into other applications (Manual, p.49)
- Selecting the position (below or above thumbnails) and detail of the EXIF data to be displayed in Grid mode (Manual, p.161)
• Abridged exposure data (shutter speed and aperture)
• More complete data (shutter speed, aperture, ISO, exposure correction)
• Date & Time (from the EXIF data)
• Camera name
https://www.fastrawviewer.com/blog/FastRawViewer-1-4-release-candidate