I've never used the iGPU on my old CPU. I just never needed it. And yes, I purposefully bought the same CPU generation and the same socket and manufacturer mobo, JUST to avoid this type of issue. Also, I don't see the need to spend double the money if AM4 and 5th Gen AMD has been working fantastically for me.
There is a small chance you'll have to change your fstab depending on how it's configured; if it's done by drive UUID, it won't be a problem.
This is the part that worries me the most. I don't know much about this whole UUID stuff (I'll learn of course). I HAVE moved ssds between machines before without an issue, but that was all Linux. This time it's a dualboot