I was there between Christmas and NY in 2022 in Tromso. It was very cold (and unbelievably dark, even during the day) The suits they provide for the activities are superb though, just wear normal stuff underneath, they keep you really warm. They are big enough to fit a down jacket underneath but you likely won’t need to. They give you good boots too.
Walking about during the day in jeans with a jumper and down jacket was fine. Night time ok too as restaurants and bars etc are all heated. The only time I was properly cold was a northern lights bus tour where we got out and waited for the sky to do its thing.
I’ve done multi day hikes in the past, mountain stuff (Kilimanjaro and Mont Blanc) and didn’t take any of that gear I used up there. In hindsight if I were to do it again I’d take a merino base top and leggings for the NL tour but that’s all I’d change. IMO you definitely don’t need ski pants or over trousers.
Footwear wise I took a pair of Air Force one high goretex, the “winterized” edition with the rugged sole and they were perfect. Again I don’t think you need proper boots.
Take plenty money with you though and some heart medication for when you see the food bills in restaurants