Microsoft says you should buy a new computer if yours is more than 3 years old, since Windows 10 might run slowly on older hardware and won't offer all the new features. If you have a computer that's still running Windows 7 but is still fairly new, then you should upgrade
Completely unnecessary. Any Intel based system running a 4th Gen Core i5 or i7 processor will run Easy Worship Windows 10 quite well with an appropriate graphics card and an SSD. Any 2nd Gen Core i3, i5, or i7 or later will Windows 10 just fine, but I would recommend using an SSD instead of a spinning rust hard drive. While i3s in general and 2nd and 3rd Gen i5s and i7 will struggle with EW to some extent, they will still function extremely well as basic office or every day computers. It's the more demanding tasks like Video Editing, 3d Modeling, Projection like EW or ProPresenter that could cause some issues.
As far as AMD systems go, anything older that Ryzen architecture should definitely be replaced except for the most basic tasks.