What are impressionistic landscape photographs? how might someone achieve them?

An impressionistic landscape carries with it a vague or elusive sense of reality. So impressionistic photographs will make the landscape seem more unreal. You can best get these photos at golden hour,  there are some techniques you can use, like intentional camera movements.This technique works great on landscapes such as the horizontal lines in a beach scene. Selective focus and focus through are my personal favorites. Here is a link for some good tips:
https://digital-photography-school.com/5-impressionist-photo-techniques/