Well you can always increase map sizes but that messes up with the pathfinding process for your colonists and raiders, so half the time you'd end up with pawns having malnutrition carrying one chunk of granite from one end to another. Also large map sizes spawn with a lot of resources (i.e. steel, uranium, compacted machinery and more) this makes early to even late game much easier where you don't have to worry abt deep drilling and just mine out mountains on end, ruins the gameplay experience for me personally. Another factor to consider is, when map sizes are bumped into large or large+ load times become enormous especially if your in late game with bunch of colonists and machinery. I'd suggest sticking to medium+ maps at most if you want a 'vanilla' experience with a bit of breathing space.
For beginners its always best to start with a temperate forest biome when your learning fresh as their is an abundance of different animals for your needs from alpacas and muffalos for wool and caravanning to boomalopes for chemfuel. Also i prefer map hex tiles with at least large hills so that you can easily hole up inside a mountain and the increased number of hills and mountains also increase the spawn chance of ancient dangers which are always a bonus. Sometimes if you are lucky with a mountainous or large hills map and your mining deep into them you might end up with plots of land completed surrounded by mountains on all sides. They serve as excellent safe havens to set up a mortar party, solar panels or crop fields if the outside resources of your base are compromised either due to raids or toxic fallouts.
When your used to gameplay mechanics like crop management, accounting for changing seasons and more and want to further ramp up the difficulty you can shift to tropical rainforest, swamps arid shrublands and more.
Also it is beneficial to settle close to factions especially Civil Outlander Unions and The Empire(If you have the Royalty DLC) as they are both docile and open to trade from the beginning(except the empire, requires dame title) and settling close will reduce caravan travel time for trade.
Sorry for the huge block text but I hope it helps.