What are the main similarities and differences between the present China and the present Ukraine political situations?

The American Congress’ Speaker of the House of Representatives, Nancy Pelosi, has today (2/8/22) landed in Taiwan, against China’s wishes. China is therefore about to start “live fire” military exercises around Taiwan.

In Comparative Politics, what are the main similarities and differences between the present China and the present Ukraine political situations?

Note that the question is asking for a comparison of two political situations, not a comparison of two different countries.