It is common practice in forums, that members can't delete whole threads, so this is not a bug.
Even when using forum search function seem not to be common practice these days, this thread has still valuable information, that I not want to delete it.
Maybe this has changed, but last time I checked the Windows build server environment, it was not possible to get a community Qt version with 64 bit MinGW.
So there is currently no 64 bit version of LibreCAD too.
Beyond that, I don't think that a 64 bit version will bring a big performance boost.
So when you have performance issues, there can be several other causer, which we can discuss when you give us some more information.
investing less than half an hour into Search function can save hours or days of waiting for a solution