The Flex example I did was a Ordered List <ol> because the radios were numbered. I removed the list style, but replaced the numbers to the end using a css counter. But as far as html is concerned, its a regular ordered list.
In later examples, you name the radios, so maybe use <ul> instead and remove the counter.
The point being, I offered this days ago, it’s valid, semantic, slim and very responsive without the need for any media queries. Yet this is still going on, messing around with 90s style table layouts and suchlike.
You may wish to tweak the styling, but it’s quite a complete solution, if I do say so myself.