First and foremost, the user that adviced you to look at the connection speed is 100% right. If you establish a gigabit link with a gigabit device, it makes no sense to upgrade other than future proofing.
There's no point in going beyond Cat 6a. Keep in mind that the length of the cable is a big factor as well. For 1/2.5GbE, Cat 5e is plenty (for at least 100m). If you plan on going to 5/10GbE now or in the near future, Cat 6a will get you there with ease (for at least 100m). In both cases, keep the cable as close to the required length as possible + a 30cm/1ft service loop (slack) on each end. That will cause no more signal degradation then necessary and make for a clean install.
Windows 11. It came with a license, I'm depending on the Adobe Suite and several productivity tools that run trouble free on a Windows machine. My instance has been cleaned up by Windows 10 Debloater and Shutup10. I feel like I need to make excuses for using Windows but when it's set up properly, it is very familiar and intuitive. Plus, whenever you get new equipment or need a niche plugin, you can count on it that they'll have a well maintained Windows application.