If you had to pick a laptop or mini-PC, which one?

You wanted functionality with a myriad of streaming services, I just use Quboz and local stored files. Linux on the box  and control apps on my tablet suit me. 

I have no idea what laptops you're looking at but here's one about$400 that would do everything you want. 

https://www.dell.com/en-us/shop/dell-laptops/inspiron-15-3000-laptop/spd/inspiron-15-3593-laptop/nn3...

Huh just looking up deezer it doesn't use Wasapi or ASIO? Strange. 

What DAC do you use,  most newer ones with asynchronous USB already reclock. 

To stream music yes it's more than enough. Put your music on one of these. The laptop I linked has a card reader

https://www.amazon.com/SanDisk-256GB-Extreme-UHS-I-SDSDXXY-256G-GN4IN/dp/B07H9VX76D/ref=asc_df_B07H9...

The I mobile CPU is built on 10nm tech the U on 14nm. The U has better graphics and few other things that are not relevant to what you’re doing. There isn’t that much difference for what you want to do which is stream music you can do that with a celeron. For 100GB of music I wouldn’t waste money on a NAS. I keep more than that on a flash drive. You don’t need 16GB of ram I run a NUC with 8GB and do DSP conversion. All you said you wanted to do is stream music go whichever way you want but simple streaming isn’t taxing a computer.

I use a flash drive connected by USB I never have had any problems. I imagine the card reader is connected to internal USB bus or PCIe.

Are you going to use the laptop for anything other than streaming music?

NUC is a computer, streamers are basically computers optimized for one purpose so it won't have as many processes running the CPU is usually ARM based, less noise which might be noticeable. I use a NUC and I never noticed the sound being worse than a Node2i with external DAC or an integrated amp I had with streaming built in. 

You've been using a computer does it sound bad or noisy? 

I don't use windows. 

If a windows laptop does everything you want now I would look at a new laptop. No need to spend a lot if all you do is use it for streaming. You could even get a refurbished Dell desktops on Amazon around $250 including Windows 10.