Yes the Core i9 will be an overkill for most of the users. Processors like Pentium and core i3 or even i5 with good clock speeds and RAM will be enough for doing daily office work.
Which Intel processor is better i7 or i9?
The Intel Core i9 is a much faster processor than the Core i7. The i9 has a base clock speed of 3.5GHz and a turbo clock speed of 4.8GHz, whereas the i7 is 2.8GHz and a turbo clock speed of 4.2GHz. Additionally, the i9 has a max cache of 16MB and max memory support of 128GB.