I have never visited northern Sweden, but if it is anything close to northern Finland the soil can't really be called tundra. There's huge amounts of forests with grassy soil. But then on the other hand winters are cold so the overall "crop yield" throughout the year is closer to tundra than grasslands.
I would guess Mongolia having huge areas of tundra because they are in the middle of a huge continent without any seas nearby and winters can be super cold.
EDIT: Forgot the actual topic
Tried Sweden on Emperor. Didn't really know wheter to pick tradition or piety, so I went piety with tundra faith. Was planning on gathering faith and going Glory of God reformation and buy every great person there is. Game went well overall except the slow growthrate. Only had couple of deer and sheep nearby. Sweden has its upsides, but the tundra can be tricky as mentioned before. Try it.