Can you show an image of stat gpu ?
And UEs multithreading is limited (you have mainly two threads, the game thread and the draw thread, so if you have a multicore CPU the CPU usage shown in the task manager will always be low) and I don’t know what the GPU usage in the task manager means, even if I’m GPU bound in my project it only shows a couple percent GPU usage, whereas nvidia-smi shows 98% usage which is more likely =)