2TB NVME. They’re reasonably priced now and the performance is worth it and you’ll have enough room to last a few years.

Plus, if you use Fulcrum (recommended), it adds another 100GB+ of indexed data.

This NUC plus a 2TB NVME and 16GB of RAM is a pretty good deal and isn’t much bigger than a Raspberry Pi 4 and at current prices, it isn’t much more expensive either.