Question CPU Bottlenecking Download Speeds?

[Gamefreaknet]

Full Specs:
i7 8750H with UHD 630
Killer AC1550 Wireless
Killer E2500 Gigabit Ethernet Controller (comes up as Qualcomm Atheros 1000mbit controller in Hwi64)
RTX 2070MQ 8GB
3TB (2TB NVMe and 1TB SATA III drive) SSD (around 1.5GB free)
32GB RAM 2667mhz (2x16GB)
Mobo: Alienware 03R2RY - Intel HM370

I have my laptop connected by a Gigabit hub running through a CAT8 cable (yes I know the issue with some cables being fake/not up to spec) and have tested on my desktop which achieves around peak of 950mbps download however whenever I try a download on my laptop with the same cable my CPU will spike to 100% and flat line at 100% until the download finishes getting a peak of 600mbps?

 

[rgd1101]

ssd is too full.

 

[Gamefreaknet]

ssd is too full.

Both SSDs have around 700GB space left though? I thought the point before SSDs get a performance impact due to being full was 100GB left or less???