There are two main groups of XC skis. The ones made for speed and use in pre prepared tracks, plus the ones suitable for 'off track' skiing.
The 'speed' ones are around 4-6 cm as you say Billy, and the 'off track' are wider. The ones I have are something like 9cm wide. Perfect on very loose snow, with a load on your back.
I threw away my speed skis decades ago.
The bindings are different, most speed skis use bindings where a specific shoe is used.
(My Vintage army bindings are suitable for Telemark skiing, which is useful.)
I suspect rental skis are a little bit wider than the 'speed' ones, with a more classic binding.
Narrow skis = difficult with the balance for beginners.
The prepared tracks should be fine with the wider skis. Specially in tourist areas.
Just be prepared, you will fall a lot, but snow is soft, and a tree bole is a good way to stop you in an uncontrolled downhill excursion!