pfr Yes, 8GB for /var is too much, run pkgin clean after updates/upgrade and you'll be fine with less than 4GB. Also, 12GB for / is a bit too much, you'll be fine with 6GB. The amount of swap depends mainly on your needs for suspend/resume these days.
Now, only you can judge the size of /home but, only 20GB for /usr feels a bit restrictive.
Do you plan to build stuff with pkgsrc? In that case it wouldn't hurt with some extra space for /usr. I have 16GB total, 2.6GB used in /usr without pkgsrc but, sometimes I've found myself setting it up and it grows to 4GB in size. Add to that setting up the building tools, possibly the wip repo and some build time dependencies, you're easily up to 9GB of used space. I have only a 30GB SSD on my machine, so I build one package, install it and run make clean, make clean-depends but, if you have enough room it would be good with 30-40GB for /usr.
If you already know that you won't be using pkgsrc, than 20GB is enough 😉
No, it won't ask you for /tmp, and you don't really need it (unless you know you do), it will use free swap space for that. Actually, NetBSD doesn't ask you anything 🙂.
