360 video stitching performances depend greatly on the CPU and GPU configurations.
CPU is used intensively for encoding/decoding videos. An high end CPU is recommended if you intend to decode multiple 4K videos for high resolution stitching resolutions.
GPU is used for image processing. VideoStitch leverages CUDA, which is available on nVidia's GPUs.
If you intend to stitch 4K+ resolutions, a GPU with 3GB of graphics memory or more is recommended. This isn't uncommon nowadays, high end GPUs provide up to 12GB of graphics memory.
Processing speed depends on the amount of CUDA cores, their frequency, and in some cases, on memory bandwidth : How to chose your GPU ?
Whatever your needs are, try to build a balanced computer. Do not pair a high-end CPU with a low-end GPU or an integrated chipset: the performances will be capped : How to optimize your computer for VideoStitch ?
If you need specific advice, we welcome your questions in the forum : http://www.video-stitch.com/forum/index.php?page=Board&boardID=7