We're moving and I will finally have upload speeds greater than 3.25 mbps.

Provider is Midco.

Home is a 3 level--walkout basement, main level (where modem/router will be based), and upper level.

Most of the devices will be main level or basement.

20 YO home, standard wooden construction.

I will buy my own combo device, the Netgear C78000 seems like the most powerful with best range.  Where to find at best price?

I'd think about a modem and separate router/mesh system but you'd have to walk me through it very slowly.  

Not sure why you didn't post in Urban Commandos section but I'll give it a try.

Don't get a combo modem/ router.  Both are compromised to fit in the same box.  Find a modem on your ISPs approved list.  I used an Arriss for years.  Then get a separate Wi-Fi router.  This will allow you to move the router to different rooms for the best coverage.  My modem was in my office over the garage but the router was centrally located in the living room.

Never been in urban commandos, didn’t know what it was.  

I’ll check it out