Solid core OFC vs stranded OCC copper

for what application?

Stranded copper because it is far more flexible. IMO there is NO sonic difference between stranded and solid core.

I use solid core for internal chassis wiring and stranded for everything outside the chassis.  I do a lot of DIY stuff, so that makes sense to me.

I'm same as spatialking. using stranded for internal can be issue with extremely small gauge wiring, frying individual strands when soldering. As for SQ, no overarching reason for one over the other IME.

Certain patented cable designs favour stranded cables ( eg CARDAS)

Both the Clear and Cross lines feature Golden Ratio scaled, ultra-pure copper multi-stranded Litz conductors, carefully chosen dielectric materials, and innovative manufacturing techniques.Cardas litz conductors use ultra-pure copper, in a Golden Ratio scaled, multi-stranded arrangement. Each individual strand is coated in an insulating enamel.

Litz conductors must be tinned before they can be soldered to a circuit board or a connector. At Cardas Audio, we remove the outer jacket with hot tweezers, dip the wire in Cardas Rosin Flux Soldering Paste, and then hold it in a solder pot for several seconds, until the end is tinned.

The Clear line refines the design principles found in Cross, with new discoveries in metallurgy and termination techniques. Clear cables have Matched Propagation conductors, in which the propagation rate of the conductor is matched to that of the dielectric, as described in George’s latest US Patent, #7,674,973.