There is no city simply named "LaPaz" (one word) in Mexico. The correct name is La Paz (two words), the capital of Baja California Sur state, located on the southeastern coast of the Baja California Peninsula, facing the Gulf of California (Sea of Cortez).
La Paz, Bolivia – Administrative capital of Bolivia, world's highest capital (~3,650 m / 11,975 ft). Entirely different city, continent, and context.
If "relative size" means compared to other Mexican cities: La Paz is a mid-sized regional capital—larger than Loreto or Guerrero Negro, smaller than Tijuana, Mexicali, or Cabo San Lucas (metro). It's the 4th largest city in the Baja Peninsula (after Tijuana, Mexicali, Ensenada) and the largest in Baja California Sur.
For travel, La Paz (BCS) is served by La Paz International Airport (LAP) with domestic flights and seasonal US/Canada charters. It's a gateway to the "Aquarium of the World" (Cousteau's phrase for the Gulf of California).