If I activate this feature: https://xtemos.com/docs-topic/show-single-variation/, it will turn ALL variable products into single variations, correct?
Is there an option to do this only on a per product base? So I choose which products? Or which product category? Or which tag? Or somehow?
I do not want this for ALL my products, just for some.
Unfortunately, right now there is no options for that. You can create a ticket here: https://woodmart.canny.io/feature-requests so our developers will consider such a feature.