Hello,
The i9 is, in fact, not a typo, and is far ahead of its time. In a laptop cooling just isn't enough. In desktops not so much - but in the laptop form factor it is a 45 wat chip that has 8 cores and 16 threads. Intel is getting far too big for its britches since most Windows applications that we use on a daily basis are not optimized for multi core usage apart from video or audio editing.
That said, 16 GB of ram is beyond sufficient for someone who is simply doing office and web browsing tasks. In 6 years it may become equal to the 4 GB we have now, but generally with a fast NVME solid state drive you're going to do just fine regardless of i3, i5 or i7. An i5 is a nice compromise though and I'd certainly recommend at least that versus the i3. An i7 and mechanical drive is going to be a heck of a lot slower overall than an i3 with that fast ssd. These 8th and 9th generation Intel processors are already ridiculously fast and we're at an age when programs need to become optimized to take advantage of the power we have rather than the opposite.