Feel free to delete them. Separate major versions of Adobe products don't interact and install in separate locations. Just be aware that you will have to reinstall the CC stuff since deleting older versions after the fact messes with file associations and shared components.
You can delete the Photoshop versions install tree from something like windows file explorer or even use system command line command. Doing it that way some junk may be left your system configuration Sill you system will run and Adobe un-installer will not mess up your configuration to the point you have to reinstall newer versions or fix up many file associations. I had cases where I had to reinstall that what I had use Adobe un install on because even reinstalling the newer version I still had problems with droplets. From then on all I do is delete the older version install tree to recover space and use a registry cleaners to get rid of the rat droppings.
Adobe un-installers should look at what it is replaceing in the refistry verify what is being replaced is something the was done by the version being remove installer.
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