I should note since the last fornite update, epic specified in the patch notes that they increased the dynamic resolution on Switch, which might have some effect here. Switch version definitely seems to have been helped by better optimisation and very good native unreal engine support considering Nintendo was looking that engine to run on Switch from the start, even using it for their own games such as Yoshi.
"Significant GPU optimization on Switch. Moved to the high-end forward renderer. This increases dynamic resolution by 10% in expensive scenes."
https://nintendoeverything.com/fortnite-version-5-20-patch-notes/







