Which is best for Blender?

Does anyone have benchmarks for top end cards, RTX 2080 ti / Titan RTX etc?

Blender Open Data

In terms of cost per system, the comparison here would have a meaning if 2x2080ti’s were compared to 1xTitan RTX. And of course two 2080ti’s would win

Can there be shared Memory?

I think for now only e-cycles gives this option via nvlink

I am pretty sure regular Cycles has NVlink support as well. Perhaps only 2.90, though.

https://developer.blender.org/D7426