If I have a high FP64 GPU then I assume it would be similar to the current WU, in terms of speed up?

There is an "anomaly" in the latest version of BOINC client's use of tasks that use the GPU option. It has something to do with the Intel GPU. It can hang a task indefinitely. Trod carefully before checking this out. As Redbeard the pirate might say if he were still alive, "Matey, ye be warned!"

To clarify, running the GPU was testing doing the same task as the CPU. AMD GPUs from a purely teraflop performance standpoint should preform much faster than the RTX 3070 when simply looking at spec sheet as AMD invests more into this feature, however it remains to be seen weather this advantage will be realized in practice. The main idea here is to recognize that if the GPU and CPU are doing the same amount of work and an average computer has both a GPU and CPU; it is likely to double the amount of computation preformed overall on part of the network. I would like to point out that, although this slightly effects CPU performance, it is a minimal cost as the CPU section of the GPU code is designed to be lightweight and serve only for control purposes; this fact was realized when testing running both at the same time. If anyone wants to get an idea of performance for their specific system, the Github repo does have a working version of the GPU code although it does not support as many features like the LMC at the moment.

If the GPU version is doing the same work as the CPU version in roughly the same time, then, no, don't distribute it. GPU versions have a habit of also needing some CPU, so the net result is some CPU plus a whole GPU for the same effect as a CPU. Waste of resources.

The comparison specifically preformed was between a i9-10900k and RTX 3070, using all available compute cores for both.