Are there legacy versions of these plugins still available somewhere?
If so where?

First time I hear about sound changing, a problem with lost settings happens with dev tools/framework changes which I believe is the case here, so if you were using the VST2, try to keep it and add the VST3 for newer projects.
It wouldn’t be a huge problem if Tunca (the dev) would change the plugin ID when it happens, but unfortunately he’s not.
More renowned devs sometimes make the same mistake. I still use an older version of TAL’s Vocoder because the way side-chaining changed too much for my use. If the latest version were using a new plugin ID they could coexist and all would be good, but nope. Life has to suck. :/

The legend says every time he updates the plugins, the sound changes. What do you think about that?

Which Ronson are you referring to?

The main difference I see is the removal of a VST2 build and the inclusion of an AAX build instead (Windows). The VST3 is clearly not the same build, filesize, crc32, etc… And is distributed in the folder-tree kind instead of a single .vst3 file.
More investigations are needed. :)