Even studded tires overly wide will compromise snow/ice traction due wide contact patch and less pressure per area and less "pressed in studs into ice". On snow wide tires will "float over snow" without digging in to more harder packed pavement with more grip, similar to aquaplaning. There is reason while even very powerful with forced induction WRC rally cars run almost-space-saver-looking skinny 15x6 to 15x7 wheels with width of some 155-205 (with tires often have reduced/smaller actual thread width of eg.
147mm or
159mm, smaller then supposed tire "mount-width"). So either you don't take out on snow/ice on subpar chosen for looks only too wide wheels & tires and keep car garaged for winter, instead of asking for "winter wheels/tires", or better choose something reasonable, that will provide some traction for safe & reliable enough driving despite whatever winter in Finland may throw at you. Given that often for bigger wheel sizes tire manufacturers just not making narrower sizes, imho worth -for winter- to either choose the narrowest tire released for used wheel size, or maybe get dedicated winter wheel set of smaller size. If nothing else, even steelies may do, if budget is tight. As side bonus for smaller diameter wheels tires too will cost noticeably less, and also will provide extra ride comfort/compliance over bad roads and extra wheel protection. For frequent snow/ice i'd get studded tires (imho should be legal in Finland). Eg. new Michelin North X-Ice 4 or Nokian Hakkapeliitas 8 or 9. Of narrowest width you can get for wheel size (but your current mentioned 18x8.5 sounds very bad choice for that, as not only R18 tires will cost much more (if that can be of indicator, for me set of Hakkas8 for R16 wheels was 150eur cheaper then almost same set for R17 wheels), but also any good for winter roads tire widths will be too much stretched for that wide of a wheels). My choice for winter would be getting R16 wheels + 195 or 205 wide xin4 studded tires so i can drive safely when i want or have fun like
this.