General feedback,
This is not an issue related to Windows 10 per se with Spectrum TV.com. If you are trying to get Spectrum TV to not be pixilated and jittery, you need at least 8GB of RAM. My Windows 8.1 PC that I got as a gift at then end of 2014 was a $300 Best Buy budget model. It has only 4GB of RAM. There are limitations within the processor itself that it can't handle Spectrum TV.com very well. Full Screen Video has been jittery for years. Sound is OK. But users really need the amount of memory recommended above to enjoy Spectrum TV on any Windows OS.
In contrast, my Windows 10 PC handles Spectrum TV like a dream! 8GB of RAM and a fast processor. Now, I need to say that I just got auto updated to build 1803. Remember that Windows 10 is a service, and updated builds are released with new and modified features, like it or not twice a year. The goal is to support Windows 10 according to Microsoft for the life of the device on which it runs. There will not be a Windows 11. When your hardware gets old, and your computer starts to die, your next computer will still be Windows 10 with the latest feature enhancements.
However, with Spectrum TV, the issue is having enough RAM on your PC, phone, or tablet to support the video processing at the site. I support a move to HTML-5 technology for Spectrum TV, as its current Flash based technology has its own security concerns. Windows 8.1 and Windows 10 auto-update Flash. Windows 7 users should make sure that the check for updates feature is enabled in Flash Player. It is possible that a move to HTML 5 technology will make Spectrum TV more reliable.
FYI I don't have Chrome installed on either my Windows 10 PC or Windows 8.1 PC. (Too much of a memory hog, over the preferred Firefox that uses less RAM.) And the Quantrum version is said to be 30% faster than Chrome.
The user running Windows XP should SERIOUSLY consider a new PC. You are running an OS that is seventeen years old, and prone to all kinds of security threats. (Windows XP was never built for security.) I would look to spend at least $500 for a nice machine. If you get a budget machine, they load those up with crapware and you are prone to slowdowns and reliability problems.
Satch