I've tried different kinds of guitar strings on my nylon guitar. But they are all High tension strings. "Hannaback 815 SHT (super high tension), Savarez Super high tension, Knobloch ACTIVES Double silver High Tenstion and D'addario high tension.
The guitar I used on these vidoes is a Sandén Nylon string guitar.
It's 48 mm at the nut and 60 mm where the neck meets the body.
Hope this answers your questions!! Have a great day /Emil