If you're a non-gamer, then you don't need either an i5 or i7, you can make due with a Pentium, or an i3. Even a Celeron will do. The only reason for getting an i5 or i7 is the extra performance and cores required for a game. Also if you're not playing games, then there's no need for any more than 8GB of RAM. So if you're choosing between 12 or 16GB, then 12 should be more than enough.
However, an SSD is more than worth it, no matter what, playing games or not. SSD's make the entire system much more responsive in general in every way! I would recommend getting an 250GB SSD or bigger, and pairing that with a 2TB hard drive or bigger.
The i7 and 16GB RAM will be better if you plan to edit videos, do any animation or CAD, or livestream anything. If this is just for typical use (MS Office, browsing the internet, etc) even a Pentium G4400 with 4GB RAM will be more than enough. The SSD will make the computer boot a lot faster and any programs that are installed on it will load a lot faster. If you can afford one, get one.
My FIRST choice would be an SSD – 256G is good. add a conventional drive for your documents etc.
An i5 CPU will be more than adequate. RAM isn't dear so I'd fit 16G to ensure the page file doesn;t add wear to the SSD.
Choose a mobo with good on-board graphics – you can always add a graphics card later if you feel you need one.
And get a good case and PSU, and quiet fans, they WILL last a lifetime.
For non-gaming, an i5 and 8GB (12GB) is more than enough. Once you start into gaming or heavy video use, then a better video card is more important than an i5 or i7.
SSD makes the Windows boot faster, and load applications faster. However, once loaded, the system runs at the "usual" speeds (CPU/Ram/Video limited)
i5. 8 or 12GB is normally enough. An SSD is well worth it.
I would recommend the i7 with 16gb ram if you can afford it cause it gives the best performance
17, 16gb and an ssd are good