New Rock install

I’ve just installed Rock on a Nuc 8i5,my previous setup was on a Mac mini .I know I shouldn’t get better sound quality but I swear blind I’m getting a less boomier more controlled bass.I’m very impressed with Rock/Nuc setup.I have a couple of questions.
Nuc to endpoint Cambridge 851 which is better
Nuc to 851 Direct USB or using Ethernet (cabled)
I have 4 tb of flacs on a usb powered spinning HD would a powered HD be better on USB .Or would a ssd inside the NUC be better.
If I went with the Nuc usb to 851 I would need a fan less case what would you recommend ?
Thank you for any reply’s in advance

ad 1 Nuc to 851 Direct USB or using Ethernet (cabled) //i guess nuc - eth - switch - eth - cambridge could be better option, but suggest to try both and compare //
ad 2 HDD vs SSD (internal ssd would be litte bit better, but considering the cost of 4T ssd i would spend money on other parts of system)
ad 3 case - akasa turing

Thank you for the reply,I went the whole hog got the Akasa Turing,4tb evo.So glad I did,ultra fast much better seperation than the Mac.Easy install of the Nuc,the only thing to slow the whole process down was putting 4 tb of flacs onto the internal ssd.No other way than over the network.