Yes (on Steam). Steam will download the base game first, allowing you to play the opening tutorial mission while the rest downloads in the background. However, performance may be choppy until the download is 100% complete.
You can manually reduce the game's footprint by about 10–15 GB if you delete unused language files located in the game's days gone download size pc full
Curious how the PC version stacks up? The PC port is actually larger than the console versions due to higher-fidelity assets. Yes (on Steam)
An NVMe M.2 SSD is ideal. A standard SATA SSD is excellent. Only use an HDD if you have absolutely no other choice, and expect a noticeably rougher experience. and expect a noticeably rougher experience.