Hi Marta, gutentag, nice set up! Walls look great! I got Tansy and other things you mentioned. Tansy is great, it does spreads outwards, i was worried mine wouldn't get bigger the first two years, but it did and now it's six times the size. It's standing next to another plant that spreads, don't laugh it's called black horehound, which is very common, but attracts so many of the smaller cute flying insects from august till late autumn i wouldn't want to get rid of it. They keep each other in check. Or i dig some out to put on the compost with my hori hori, or i keep cutting it and using it as a mulch. Which keeps the earth much wetter, saving watering and enriching my soil biomes. Millefolium spreads through seeds as well, i'm less happy with that, as well it grows agressively through rootstocks, it's work to keep in check.
I can't really say if it repels insects and plagues really, but all this biodiversity in plant life in general does attract biodiversity in insect life, and many a time, i noticed in my garden a newcomer arrived that keeps some kind of "pest" in check. The bio diversity in insect life makes that a biodiversity of birds come into my garden, dropping manure all over my garden, making my plants grow, when i keep them in check it's feeding my compost piles, leading to easier gardening.
I had a very bad infestation of aphids on my peach trees, when the frost had killed of all my blossom. It was horrendous. I didn't notice until the flies started buzzing every time i passed there. They were there because the ants had been moving aphids like cattle, creating a ant paradise, sugar droppings every where. It was able to get this bad, i reckon because there was no fruit that year, leading to a boost in fresh green shoots. Anyway, i decided not to care, because i had other stuff to do and don't want to be busy with aphids. So i observed and noticed first huge flocks of ladybugs arriving, then they ate the aphids, but it was too big of an ifestation, they couldn't get it under control, the parasitic wasps came and laid eggs inside the aphids, horrendous, but that's nature, it was full of these, then some other aphid eater came to flourish.
Next year, no frost, no aphids, record peach year.
I noticed these aphid eaters have found a place to survive in my garden, somehow, thanks to my biodiversity, i got more than 200 plant species in my small garden and thanks to not cleaning everything like it should be humanwise, i got piles of stuff rotting away here and there.
I hope this answer helps you a bit.