Pants and hardshell

I would give serious consideration to a softshell pant, you want maximum breathability (unless touring in a downpour is likely). I usually carry a hardshell jacket but rarely use it. I’m more likely to skin up in a softshell jacket and throw a puffy over it when I get to the top (mine is slightly oversized to fit over my gear). I toured Svalbard a few years ago in April and that worked out fine for me (never used the hardshell). Spend some time touring at a resort and work out what layers work best for you. Even on the coldest days, I wear very little on the up (a synth base layer & softshell fully vented). Your goal is to minimize how much you sweat on the way up. Also, check with the guides where you plan to tour, they will usually have a good gear list.