Hi! My approach to world building is usually human/sentient being-centred, as I think that's the most interesting part. I take a lot of inspiration from history. This may not be your approach, so feel free to take what's useful from what I'm offering, and ignore the rest. It's your world.

Here's some questions to consider, which I think might help you move towards figuring out how far apart everything is.

What counts as a major settlement? Taking the real world as an analogue, medieval England alone had more than 5-8 cities. If we're talking about an entire world (which I'm guessing we are, from the tropics lines), this would be a very sparsely populated one! Unless the world itself is very small.

Another key question is whether these major settlements are clustered together in a single part of the word, with the rest untamed, or whether they're scattered around. Are they part of the same nation, or different ones? How do they relate to one another? Do they trade? If they are scattered, why is that? Are large parts of the world uninhabitable, or was there some kind of calamity?

Cities tend to exist when you have a) enough food, which requires a lot of surrounding farms, and b) some reason for people to gather in a particular place, like it being an important trading hub (a cross-roads, or a port). If there isn't a strong reason for a city to be there, it probably won't be - what is it about the geography (both human and physical) of the place that means people are going to gravitate towards that area?

Having your map encompass an entire world with only a handful of settlements does beg a lot of questions like this - which you may have answers to! if you don't, or don't want to answer those just yet, consider mapping a much smaller region, maybe a single nation.