Where i live it is almost always dry so i ride tyres like maxxis Ikon.
If on a rare occasion it is wet, and the ground is very sticky and clay like, should I…
Run as low a pressure as possible to get more traction, or…
Run high pressure to cut through the mud more.
My main problem is the knobbs filling with mud and everything getting very heavy! (if it rains)
Generally lower pressure is better when wet to aid with traction on slippery rocks or roots. Howerver I don’t think it will help much with the mud issue. For wet mud your really need larger, wider spaced nobs for both traction and mud shedding. The Ikons are going to clog up for sure.
If you are riding in a season where conditions are variable, something like a Nobby Nic is a good option. Its still quite good dry, but will handle mud better than an Ikon.