Clearnet and Tor settings in Bitcoin Node

I was wondering about the default settings of outgoing connections. On default you have outgoing connections to Clearnet Peers as well as Tor Peers and I2P Peers. You could also choose “Make All Outgoing Connections to Clearnet Peers Over Tor” but it also says “Connect to peers available on the clearnet via Tor to preserve your anonymity at the cost of slightly less security.” Wouldn´t it be better to make it only available on Tor? But what would be the “cost of slightly less security.”? What are the up and down sides of using both, Clearnet and Tor connections, or only connections via Tor? I also wonder why incoming connections are only possible for Clearnet peers. Wouldn´t that also expose the IP address of the Node?