around there are many plugins for lightroom
when installed i see they save their preferences in the lightroom preferences cc 6.7, 5 and 4 and in the catalog
when i want to uninstall , lightroom keep all the preferences of these plugins
can lightroom plugins corrupt or damage lightroom preferences and catalog ?
and can they slow down lightroom ?
It is unlikely that the leftover information in the preferences can either corrupt the catalog file or slow down Lightroom, they would probably be ignored by Lightroom once the plug-in is uninstalled. However ... you might get a much better answer if you specifically mentioned which plug-ins you are talking about.
Plugins should not slow down LR. They don't get loaded unless you use them. 99% of them are External to the actual LR program and work as External Editors.