Windows on mac

Im regards to performance, it depends on how you run it. If using Bootcamp Windows takes over and uses all resources of the Mac. RAM, CPU, GPU etc... and macOS is not running when windows is running. When macOS is running, then Windows isn't and as such it is not taking up any resources.

If using a Virtual Machine, then they share resources as they run simultaneously, and performance on the macOS side may be impacted while Windows is running,.

As to the safety of it, there's nothing unsafe about it. Regardless of how you run Windows, it is separate from the macOS side and Windows malware and viruses cannot affect the macOS side.

Yes it is safe. You can run Windows on an intel Mac using Boot Camp Assistant or using a Virtual Machine like Parallels, Fusion, or VirtualBox. Windows will run as well as it would on a similarly equipped Windows PC.