In terms of GPU:

My impression is that 18.04 is required for Vanity Search. Is there a particular model of NVIDIA / CUDA that you (or anyone) would recommend?

From the NVIDIA site the options for Ubuntu 18.04 are:

    10.2-base, 10.2-base-ubuntu18.04 (10.2/base/Dockerfile)

    10.2-runtime, 10.2-runtime-ubuntu18.04 (10.2/runtime/Dockerfile)

    10.2-cudnn7-runtime, 10.2-cudnn7-runtime-ubuntu18.04 (10.2/runtime/cudnn7/Dockerfile)
    latest,

    10.2-devel, 10.2-devel-ubuntu18.04 (10.2/devel/Dockerfile)

    10.2-cudnn7-devel, 10.2-cudnn7-devel-ubuntu18.04 (10.2/devel/cudnn7/Dockerfile)

Thanks - again!