Ardour3 supports instrument/synth plugins. Using Linux VSTi’s is supported by our own builds. You cannot use Windows VSTi’s without a special build of Ardour that provides a Windows emulation environment - our own builds do not do this, but if you wanted to go to a lot of work you could do it yourself. A few specialized Linux distributions have made such builds of Ardour3 available.
Using plugins written for one operating system (Windows) on another (Linux) is deeply dark magic, and should really be discouraged as much as possible. We know that there are many plugins that work OK like this, and that for many people, their dependence on Windows VST plugins makes it hard for them to move away from Windows software. Even so, if you really reliant on Windows VST plugins, you should consider using Windows as the platform to run them, and if not that, then a Windows program (such as Reaper) run under Wine. There is no good solution for this, other than convincing more plugin developers to make their tools available on Linux (which the Linux VST idea makes pretty easy for them).