I believe Scumhead used RGM version 5, which uses Textures at 128 x 128 instead of 64 x 64. The Resolution of the game is also doubled as well, compared to RGM version 4. Most games are made in version 4 because that version actually has more features. The developer of RGM didn't finish adding back all the functionality into version 5 before they stopped working on it.
As for Fullscreen mode, I believe you can make any RGM game open in fullscreen if you do the following:
- Go inside the game's folder, where the Executable file is, and add a Text document into that folder. It should have a file suffix that says .txt
- In that text document, type "hellwomb.exe fullscreen"
- Save the text file
- Then, right click on the text file, Rename it to "Open in Fullscreen" and change the suffix from .txt to .bat
Now, whenever you want to start the game in fullscreen, you double-click on this .bat file instead of the game's Executable.
If any of that was confusing, just let me know.