What specs should my devices have to reach 100Mbps download speed?

I just upgraded my fiber internet from 50Mbps to 100Mbps for download. But then found out that most of my devices are not able to reach the full speed. I used CAT 6 Ethernet cable to connect a desktop pc to my router but it only can reach 80Mbps for download. The specs for this desktop pc is:

Processor: Intel(R) Celeron(R) CPU 1017U @ 1.60GHz

RAM: 4.00GB

Hardrive: 224GB in C drive and 224GB in D drive

And then I connect my laptop using CAT 6 Ethernet cable, it can only reach 65Mbps for download. The specs for this laptop is:

CPU: AMD E1-2100 APU with Radeon(TM) HD Graphics 1.00 GHz

RAM 4.00GB

C drive: 445GB D drive: 18.5GB

My iPhone 6 is not able to connect using Ethernet, but with 5G wifi it always reached 100Mbps for download.

Looks like the specs of different devices affect it's ability to reach the full download speed?

I use my laptop to download movies a lot. I really hope it can reach the full download speed of 100Mbps. What kind of specs are good enough for reaching 100Mbps?