I'm not a windows expert either, but I do know that there are settings where you tell LMMS where your stuff is. I used those. Real VST files all work great. My M-Audio HAMMER 88 works great with them.
As for my age, I'm 55. I cut my teeth on both Unix and UNIX(tm), using the incredibly powerful vi editor as my editor of choice, until vim/gvim came along, but strongly prefer BSD4.2 over SYSV. And rebooting any Unix (or M$) system without a very specific reason is not normal. Back before my career (electronics with a specialty in telecommunications) took a major side-step into 16th Special Operations Wing Intelligence at Hurlburt Field, FL, just down Hwy 98 from me (I was an Intelligence Systems Analyst, meaning I got to play with the cool toys that never existed ... and neither did I, for that matter), I worked with computers a LOT. At Wing Intel, I also worked with M$ NT and 2000 (plus some other Unix stuff that didn't exist). So I know enough to say that if I install something outside of the normal M$ path, I can do that. You can do that with automatic installers, too (and if something is installed with an installer, you should do your configuring there). For example, I have Godot3, IrfanView, Piskel, Vim, Tcl/Tk, and more, all installed in c:/jim/bin (some of those have their own subdirectories in ~/bin). As long as you can tell whatever's looking for it in its settings, config files, your own $PATH, etc., it's ok. But if, in M$ stuff, there isn't a way to configure that, it probably isn't safe, because M$ developers, or at least some of them, are dumb enough to hard-code stuff like that. But we're not talking about M$ here, we're talking about open source, where real brains of real users go into the development. And there is a whole section in LMMS's settings to specify where everything is.
Check it out. Look under settings. You'll see that folder icon, which means directory settings. That's where you're able to move stuff around, as long as you make sure that where you put stuff is set in the corresponding path in the directory settings.
Oh, and btw, even at Wing Intel, on my unclass and secret systems, I still ran Cygwin. I had to ask myself for permission, and I never said no to myself. Couldn't do that on the high side (TS//SCI), though...but then, I didn't need to as it was Unix.
I used Cygwin on those and my system here because the Unix command line gives you FAR MORE power than any mouse+menu does. For example, let's look for every file named foo.bar but NOT foo.bar.baz in my $HOME directory (on this laptiop, c:/jim) and save the list to list.txt. And this is just a trivial example. I could add sed and do some editing of the output, say change foo.bar to bar.foo with a simple regular expression and sed.
(21:49) % cd
(21:49) % find . -print | grep foo.bar | grep -v foo.bar.baz > list.txt
But using the command line does NOT produce different results than the (for most people, including me) much slower menus plus mouse method. It just gets it done faster (usually much faster). And that's not all. At one point, I was asked for help on something, where someone needed to change the contact information in over 100 web pages for one squadron. It took him about 18 hours on the high side, and, when I used Zsh plus vim with a macro that I made for this purpose, using search plus regular expression search/replace, I got it done in about two minutes on the collateral (secret) system. I used the right tools for the job. I got exactly the same end result...just a "little bit" faster (two minutes vs 18 hours). And for those who don't know, vim (and its graphical version, gvim) is a modern replacement for the old vi editor, and has all of the immense power of vi, plus a lot more. Like vi, its learning curve is steep...very steep. But once you get past that, its power is beyond belief. And no, please don't start a comp.editors style flame war about emacs vs vi,....