I've used Win Toolkit in the past for customizing Windows 7 and 10, and it's been quite handy for tweaking installations. As for Windows 11, while Win Toolkit doesn't officially support it, some users have reported success by using it with caution. The tool might not fully utilize Windows 11's new features, given that it's primarily built for older versions. When it comes to specific tweaks or modules, you'd probably need to test them out to see how they perform on Windows 11.
However, I'd suggest looking into more updated tools like NTLite or MSMG Toolkit, which offer robust features for customizing and optimizing Windows 11 installations. These tools are continually updated to accommodate the latest Windows changes, and they might provide a smoother experience.
Have you looked into any specific customization you'd like to achieve on Windows 11? It could help narrow down the best tool for your needs!