I think the persicaria will work well with the other plants mentioned. Not at it's best in early spring. However when it does start to flower you will have something to see for months.
I have worked as a Gardener for 24 years. My latest garden is a new build garden on heavy clay.
Pachysandra is a very useful low growing groundcover plant for that sort of aspect. Perennial candytuft - Iberis is also fine. Both are evergreen. The prostrate Gaultheria is also useful. Saxifraga urbium too. The Iberis is pretty adaptable but the others won't do so well if it's a drier soil - they prefer a decent amount of moisture to do well. I expect you get enough rain in your location though, and as long as it isn't too dry, for too long, through summer, they should be ok once established. North facing sites don't tend to dry out so quickly anyway.
It's a place where beautiful isn't enough of a word....
I live in west central Scotland - not where that photo is...
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The Iberis is pretty adaptable but the others won't do so well if it's a drier soil - they prefer a decent amount of moisture to do well. I expect you get enough rain in your location though, and as long as it isn't too dry, for too long, through summer, they should be ok once established. North facing sites don't tend to dry out so quickly anyway.
I live in west central Scotland - not where that photo is...