Hello, may I get a recommendation please on a good openwrt compatible router around $100 or whatever it costs -- that I can run Squid on as a transparent proxy?
(Note: only 2 clients at the most will be using this router)
USB port for external storage.
WiFi 802.11ac is good enough.
1 wan ethernet port. 3-4 other ethernet ports.
RAM? Doesn't matter much to me though I know a little more is needed to run Squid.
is squid still useful in a would full of HTTPS ?
Yes, you install a self-generated CA cert to use it. No biggie.
squid is io intensive... so x64 is the natural cantidate for this application
sounds ok i will have to look more into it 
I would imagine maybe a raspberry pi 4
booting off & using an SSD for squid "lots of ram"
with any openwrt router passing traffic to it
even add blocking at the same time
I like this idea
Consider keeping the old router for routing and running the proxy on a different host.
Better use TinyProxy or 3Proxy. Squid is too heavy for embedded Linux.
Also in modern web HTTPS is majority. And any proxy didn't works well with it.