With 'minimalism' in this context I mean many things, it's more of a general philosophy. I'll try to show some concrete examples.
1. avoid having a lot of installed software
Installed software is not necessarily bad in itself. But it can make troubleshooting and
maintaining a system more difficult.
For one, the system partition will take more space, which means larger backups which are less ready to be used if/when restored. Portable software on a separate partition keeps the system cleaner and you don’t have a lot of work with reinstalling software on a new system. Some programs also have extra dependencies (such as .Net, for example), which in turn might require additional software to be installed.
More software also means more potential vulnerabilities, especially with software that connects to the internet. Here’s an example with a popular Firefox extension and one with a video game.
2. avoid many running processes
Many programs have at least part of their functionality delegated to background processes, which run all the time. The downside is that more resources are being used and if anything goes wrong with a particular process (like a memory leak) it can interrupt the real-time functioning of the system. That’s why I prefer contained software that "turns off" and stays out of the way when I expect it to.
3. don’t tinker with the system (if you don’t know what you’re doing)
Minimalism goes both ways. While I actually recommend disabling some features (like in
"Turn Windows features on or off" and even some things in the System settings), I don’t
recommend doing stuff that’s too risky.
I discourage using stuff like registry cleaners or just any system cleaner. If you want to delete temporary files, there’s a Disk Cleanup tool, which is included with Windows.
Some guides might also recommend disabling a lot of services. While in theory this can have some benefits, in practice the benefits are very small at best, while it can have some negative consequences.
4. keep hardware devices to a minimum
Just like with software, having a lot of installed hardware can cause trouble. In fact, even more so.
Hardware components share some of the same data paths and circuitry. Having many expansion cards (PCI/PCIe) or external devices (USB, FW, TB) can cause IRQ conflicts. How much this is an actual problem varies from system to system, depending mostly on the motherboard's chipsets.
Hardware devices can also cause DPC spikes, especially if they’re malfunctioning or have poor drivers. That’s why it can be beneficial to disable some of them in the Device Manager (such as network devices) for crucial real-time tasks like recording.