There are quite a number of compact mechanical boards that come in ISO layout, but not so many that use Bluetooth or contain a USB hub.
Personally, I'd get an ANSI Poker 2 and a small USB hub, but that's because I prefer the layout of the Poker and like to try different switches, keycaps and cases. You can reprogram the layout, so you can find the best location for the editing keys. You can use any layout board to get the Danish special characters. I type regularly in Finnish on my ANSI layout KBT Pure and use it as my main keyboard at work for coding.
Out of the 2 you list, I'd go for the Minila Air. I have a preference for MX switches, prefer the minimalist design and you don't have to plug it in. Downside is having to replace batteries now and then, the extra weight of the batteries and getting used to the layout, particularly the small right shift and space bar.
The Matias will be quieter and has a slightly more normal layout, but it is bigger, you have to plug it in and the Fn key is in a rather awkward spot, IMHO, especially for using Home and End for editing code. Actually I'd find either of them rather awkward for editing code. I find the Fn layout of the Pure to be the best of the 60% size boards I have tried for coding. You could program a similar layout into the Poker 2....