Well, depending upon how sophisticated you are, video editing can take a lot of processing power (though, for the most part, it is I/O bound). Still, I would think that an i5 processor should be just fine for this - and is likely overkill for the simpler things like document management, email and web surfing. I have an office chock full of computers from lowly Atom processors all the way up to high-end Core i7 processors. While I can feel differences in the snappiness of the Windows user interface between the Atom/Pentium/Celeron-class processors and the Core i3/i5/i7-class processors, I cannot say that I feel a lot of differences between the i3, i5 and i7 systems; certainly no heavy lag anyway. I jump from machine to machine without feeling much difference - except when the O/S changes from Windows 10 to Windows 7: Windows 7 is *always* much snappier! (its all that spyware that Microsoft includes in Windows 10)
Hope this helps,
Many thanks for taking time to respond. It was very helpful.