To get the 10Gbps ports, you'll need one of the 12 core variants or higher. You're probably looking at around $500 just for the motherboard/CPU. I couldn't recommend these boards more highly - they're bulletproof mini-ITX form factor.
What do you think about fanless routers like DEC750: https://shop.opnsense.com/product/dec750-opnsense-desktop-security-appliance/
They claim to support at least 8.5 Gbps port to port throughput with firewall active (and it has 2 SFP+ ports, so one can go to WAN and one to a switch for LAN).
I was considering one since it looks neat and silent and doesn't eat too much power but it would be interesting to find those who use them to check how good they are.
If you insist you can get a mini pci-e card to put in any router you build. I've used these cards before. They're enterprise class access point cards and the company that sells them has a vast array of choices, up to and including the latest high power wifi 6 cards. They're all Qualcomm Atheros based and just work in Openwrt. You wouldn't want to use a consumer card. These cards are not cheap but they're probably cheaper than going with enterprise class kit, although I personally think the enterprise class kit would be a better solution.
Let's say not in the router, but putting those into a custom access point that's plugged into the switch. Where exactly do you need to put those mini PCIe cards? Into some special card / board with attached antennas? Are there kits like that for 4x4 cards? How are those antennas supposed to be shaped?