(I don't really have a definite answer, but I have some experience with this sort of thing)
VST/VSTi plugins are quite small, storage-wise, and I don't think they slow the computer down - only in the initial search and update. I always install the data libraries (presets, samples etc) to a high capacity external drive. That way, I can take that with me when I'm away and using my laptop with a smaller set of plugins.
(I have FL Studio btw and have noticed a few issues, one of which is the folder structure of third-party plugins. I created a program to fix this, but I forget what exactly the problem was - something to do with the one-level plugin folder structure in the FL UI.)
Anyway - I've always been quite fastidious when it comes to organizing my plugins - I now have a neatly organised
VST Plugins folder (organised into a huge folder tree of plugin
types). In the past, I have been annoyed by the ones you can't move about and while you could do it by editing references, it's better to just point to the correct folders on install.
But how did I move them around? I haven't done this for a long time, but when I did - I simply took my neatly organised
VST Plugins folder and copied it to the new machine. Any that wouldn't work (~10%), I would install. Once, I tried installing all these "un-movable" plugins on my external drive, but unfortunately, I forget if it worked or not. Probably not, though. But maybe it's something you could try. Obviously, the drive would need to be assigned the same letter on any machine.
But even if you just have to install them on the external drive for each machine, then only connect it when you need the plugins. I'm not guaranteeing this won't cause more issues than before, though. It's just one possible option
Note: Some plugin install executables are just zip extractors - they simply extract DLLs to your selected VST plugins folder - that's all the install process does. It's analogous to download "helpers" which just download files to your folder you could download easily yourself, but they show you ads of their newest product during the download.
As for performance, ensure you keep your system as efficient as possible, with regular clean-up routines.