is there a way to monitor when the tb connector is plugged in what the MB does
Look at Hammerspoon.
it might have a preconfiged spoon add on you are looking for. Or you can right one yourself in lua.
Present: 2012 Mac mini + PowerColor RX 56 Vega Nano @10Gbps-TB1 + PowerColor Mini eGFX 180F via Apple TB3 to TB2 + macOS Catalina 10.15.7
Something should appear in the log when a Thunderbolt device is connected. Check the log stream command. Learn about predicates for filtering the log messages.
You can turn on pci debug flags to see how new PCI devices on the Thunderbolt bus are added:
If you want to trace ACPI calls you can try using Open Core to override the DSDT with a version of the DSDT that has debug logging added to specific Thunderbolt related methods
Mac mini (2018), Mac Pro (Early 2008), GA-Z170X-Gaming 7, Sapphire Pulse Radeon RX 580 8GB GDDR5, Radeon Pro W5700, Sonnet Echo Express III-D, Trebleet Thunderbolt 3 to NVMe M.2 case