Plugins would have to go in www\js\plugins. There are a number of issues RPGMaker has had, and continues to have, because at the end of the day MV and MZ are just Javascript running canvas on a webpage inside an electron (headless webbrowser) window. To say it's optimized is putting it mildly. That said, in GENERAL this should run well. The minimum stat roughly for it is my own: an ancient Ryzen 3, and Windows 10. It may run below that, but I can't guarantee it.
That said, it sounds like your issue is less lag and more an outright freeze. I'll take a look a look at your link, though obviously I won't be pushing any bug fixes for a few days unless it's to fix something gamebreaking for most of the audience. Will definitely look into this and see what I can do, though unfortunately since I haven't suffered the issue, I won't be able to reproduce for testing. May contact you again when I've got something ready to test.