Looking for a good router 250CAD - R8500 died tonight

Based on availability on Amazon US drying up, it might be that the WRT32X is being discontinued. That is a guess without other supporting evidence.

Marvell was recently bought by NXP. It is unclear what the level of support for wireless drivers will be going forward. It could be better, or ... As far as I know, the Marvell wireless doesn't support 802.11s. See https://github.com/kaloz/mwlwifi/issues?utf8=✓&q=is%3Aissue+802.11s

If you're looking for a "going forward" solution, the idea of a managed switch, powerful router, and separate AP(s) is a good one.

Personally, I wouldn't even consider the Raspberry Pi (even the 4) as a router. I'd go with the ODROID H2 if you have budget for it. If on a more restricted budget, you might consider something like the EdgeRouter X (~US$60) if you didn't need more than around 200 Mbps with SQM (I do not own this device, nor have I tested it myself). The GL.iNet "BRUME" is an interesting mid-range option as well, but I personally haven't tested any "mvebu" (Marvell) devices. Based on reports of thermal issues and stability issues of the EspressoBin devices on Amazon (US) and elsewhere, I can't recommend them.

I personally use the EA8300 units (IPQ4019/QCA9888) as APs, selected primarily because they are three-radio units and I need to run backhaul over 802.11ac as I can't pull cable where I'd like to (or use power-line modems). I've still got a couple Archer C7v2 units in service. The EA8300 wireless is better, but when you've got hardware on the bench that works sufficiently well with current, secure firmware at "zero cost", it was hard to justify additional expenditure for a remote garage. Right now, I wouldn't spend a ton on an AP, as I expect next-generation chip sets, modulation schemes, and client support to become more affordable over the next 2-3 years.

The architecture can be found on the various wiki pages for the devices. Here's one view of devices by architecture https://openwrt.org/toh/views/toh_dev_arch-target-cpu and a "magic decoder ring" https://openwrt.org/docs/techref/targets/start