Not easy to answer generally, I tend to think indoor units are somewhat more expensive, if only because the range of split systems is larger.
PN is a bit complicated here, by now I believe both need to have over 100 posts and even then it doesn't always work. I think very few users here understand it.
I was curious about the NAT and checked your profile because of your place of residence. You practically live around the corner.
I did some calculations with the computer using the IDM indoor installation variant. It would even work with a supply temperature of 35. It would be better to aim for that in a new building.
If you don't want to remove it, you have to accept what the BU delivers. Which company handles heating at your place? They often have a maximum of 2-3 manufacturers in their range.