1. Big Sur 11.3
2. iMac 20,2
3. It's removed completely, I'm using BCM943602CDP with PCI-E adapter
4. Yes, directly to the router
5. I bought iPad mini 5 two days ago, tried Sidecar and it was laggy
6. System runs fine, only sidecar on iPad is laggy
7. Everything works fine, handoff, continuity...