End of June my wife and I hiked trail no. 403.
Basis were stages from the Carnic Alps guidebook and trace from Mapzs (
https://mapzs.pzs.si/path/139774). For hut reservations we used the website
https://www.karnischer-hoehenweg.com/ Huts were very full first five stages (to Valentinalm). Most huts cash only. Shower available in every hut, food good, shared bunks not too big.
To start in Arnbach we had arranged car transport, after end we got home without issues and quickly by public transport (bus and two trains).
First part of trail stays at higher altitude, alpine environment. But last stages also offered great views. Along the trail many small lakes, we saw some chamois, lots of marmots and diverse flowers.
No water issues on trail. Could refill at every hut, and also some spots in between.
Trail completely snow-free. Marked well (except around Mokrin), but some sections, especially second part, overgrown with high grass or bushes.
If we look at individual stages - none stand out in length or elevation. But hiking eight consecutive days can still be tiring.
Trail no. 403 is an exceptional experience. If interested, I warmly recommend it.