How to wipe everything with TWRP?

Encrypted ? How ? Why ?

Negative. My external SD storage is separate, it is mainly for music and APK installers.

Is this going to make a really clean base to re-install LOS ?
I do this since I can’t use my VPN on it, and seems that the problem comes from the system itself.

So would I wipe everything to make sure that I have a good base and see if the problem occurs again. In that case, I will downgrade to LOS 14.