Difficult to give you a precise answer because you have not provided any information about level of technology. Is this the equivalent of 1 AD, 1000 AD, 1500 Ad, or 2000 AD?
Secondly, the number of nations is a function of the population per nation. The higher the population of each nation, the fewer nations you can have given that geographical areas have a limited carrying capacities.
The basic starting point is to determine the populations of your nations, kingdoms, etc. Populations are largely a function of geography and climate. Cities require a supporting rural/farming population. A general rule of thumb up until about 1500 AD is that 80% of the population of an agrarian polity/state (i.e., prior to the industrial revolution) would be engaged in agriculture, pastoralism, fishing. So a city of 10,000 people would generally require a supporting hinterland population of 40,000. There are exceptions of course. Classical Rome (the city itself in 1 AD) had a population of about 450,000. But Rome "cheated" in that it shipped in most of its grain from Egypt and North Africa. To determine the number of polities requires that you make some decisions about population densities in this province/region you have created. You mention fiords and mountains and coastal islands. Mountainous and hilly land areas support fewer people than river valleys and lowlands/plains land areas. For example, the population of SW Norway (mountainous and fiord-y) has been much lower than the population of SE England (mostly flat-ish lowlands) for the last 2000 years even though they both have relatively similar climates. Another example: England (not the UK) has a land area of about 50,000 sq miles. In 1100 AD, the estimated population of England was about 2,500,000. That works about to about 50 people per sq mile. In 2015, the pop. of England is 53,000,000 = 1000 people per sq mile due to the magic of technology.
In closing, this is my suggestion on how to proceed.
1. pick a land area where you want to have a nation.
2. Determine the sq mi or sq km of that area.
3. Allocate percentages of that area to: farmland, pasture land, forest, wastelands, etc. E.g., 10%, 20%, 30%, 40%.
4. do some historical research on population densities for those sub-areas.
5. crunch the numbers to get a population for that nation/city-state.
6. rinse, repeat.
Hope this helps.