Let's assume it is your first game, you don't know the maps yet, don't want to bother with this aspect yet, so you choose a random generated one as many of us did. There is a few settings that you might still want to check be it by curiosity, because you love huge maps regardless of the game, etc.
- The first one is *Map Size :
It is self explanatory but note that the number written is the number of tile per nation. Claiming more or less lands is up to how you and the other players will fare in the game. * the second one is Map Tweaks
It allows you first to choose if you would prefer a map with fewer, normal or more provinces underwater. Note that unless you chose an Underwarter nation, the map generator tends to already generate a fairly high number of those provinces. Furthermore as a beginner you'll learn very quickly that underwater nation setting their sights on you is NEVER a good news for you. And it will remain true as your level increase. For that reason I'd Highly recommand for newer player to choose the fewer category. It also asks you if you'd like to enable rivers and caves. I'd suggest to keep those two enabled. The map generator usually generate very few caves 1).
Rivers are elements of the map in between province that may or may not be crossed depending on the temperature scales2), and potential bridges being generated too.
Finally, you can choose to enable East/West Wraparound and North/South Wraparound Most but not all multiplayer game will use both those settings, But it could be recommanded for a beginner not to activate one or both of them, allowing them to have one less border to worry about if said player were to spawn on the edges. It also limit your possible expansions direction. In the end the choice is yours, It can't be said to be more helpful, nor harmful.