The pricing of SSDs makes this a tricky decision for me. They're pretty much $£100 per TB - often getting more expensive as capacity increases, rather than more cost effective. Currently going over 2TB just seems not an option.
SATA is oddly expensive and slow, so Nvme + enclosure seems the way to go. You don't need 'fast' SSD because even on Gen2 you'll be limited to 1GB/s. But that doesn't matter as the cheaper SSDs are still sticking to a similar price point as most of the others.
So - 1TB nvme for $100 + $25 for an enclosure. Hmm, bit small for cold storage, but price is attractive. Go up to 2TB and you're at the same price as an internal XSX card but you're getting twice the storage. Thats good, right? But you can play XSX games off it so its really for BC or fridge management.
Finding it hard to decide the best way forward. 2TB SSD for BC and fridge, just suck it up and get the 1TB internal for more options but less space, or a 4+TB HDD purely for fridge. I don't think I'll do HDD as my broadband is fast enough that I can redownload really old stuff, so will try and stick with SSD.