Hi irishmike, welcome to the forum!

There’s no difference in quality. The numbered versions I believe you’re referring to are discussed in these threads:

Star Wars (2.7)
Empire Strikes Back (2.0)
Return Of The Jedi (2.5)

Those are the stand-alone films as MKV video files. They are available using this guide.

The release discussed in this thread are the exact same files, just with menus and special features added for burning to Blu-ray. You can find the directions for obtaining the Blu-ray versions in a guide I posted here.

As far as bypassing burning the ISOs, that’s easy. Burning them is optional in the first place. The last part of Step 10 of the guide from the paragraph above explains the following:

“ISO files are the digital images of the videos and file structures to be burned to the blu-ray disc, but it is not necessary to burn the ISOs to discs to view them. You can mount the file as a virtual drive to have your computer view the file as if it were a disc in a drive. Here is an article on how to do that in Windows. The process is even simpler in Mac OS”.

Best of luck to you and let us know if you need anymore help!