Trying to do exactly the same thing - I still have a maxed out rMBP 2013 that works great, so setting up alternatives now before I'm forced to.
The Intel Skull Canyon NUC is what I'm using, with Elementary running on Virtualbox in Windows 10 (waiting for the Samsung 960 EVO to sell globally before setting up a native install).
The one massive problem for me that keeps me going back to the laptop is that the Mac absolutely nailed keyboard layout by separating the command and control keys. And no other OS is currently able to do so.
I use the basic emacs shortcuts for navigation in all the apps that support them (crtl a,e,n,p), and the command key to issue commands like close tab, save, new tab etc.
This is absolutely impossible to replicate on any other OS (AFAIK). I can map the command key to the control key, but that's about it - it just becomes a new way to hit control. Being able to consistently map and access the command key (as SUPER) simply can't be done.