I would not buy a card in The Netherlands to be used in Switzerland unless it specifically mentions it but that's just me. Why not check the shops in your landing SUI airport instead?
Don't worry about your custom ROM unless sending the unit to be repaired under warranty & even so, some carriers do not care. Search the web for testimonials with your carrier's name.
A friend invited me to share his apartment for a couple of weeks in Zurich. I was taking out the garbage when he said "wait, you need the key for the container". I had a good laugh as SUI is known for the safety of their banks but the garbage?
He then explained that each family had their own mini-container, that they paid per volume & that some neighbors filled up his container instead of theirs if it was not locked.
