If i host a continents map in mp tiny or small size it makes 50% spawn as earth map.
It is possible to save the turn 0 and load it from autosaves, then cancel load in the setup screen and host new game, the set up will be the earth map retained but it shows up as archipelago in the map type. You can keep the turn 0 save until it gets overwritten with other games in my experience.
Had many good games on the earth map, the resources are very sparse always even if i set otherwise, this makes for a harder challenge for happiness and growth.
I started in north east china/ russian border and had only 1 wheat tile in view, no other resources. Also the good city sites are limited. Some say the map is imbalanced and that is true to an extent, but it is immersive.