You can tweak the network, to edge out a little more speed, but it all comes down to the weakest link.
That's why I have all Cat6 cabling going from my router to computers, and when run out of ports on the router (the VoIP device takes one), use a Gigabit switch, and the cabling from my modem to router is Cat7.
Now, some may find that overkill, first look at it like this. All of those cables (Newegg promos) cost less than a single 25 feet 5e cable at Walmart. Once I made the transition to Cat6 in 2011-12, at the time was paying for 10Mb/sec. Well with those new cables, my speed test results went straight from 10Mb/sec to 15Mb/sec download (at the time the next tier up), upload remained the same at 1Mbps/sec. That's a 50% boost in speed, and to see if I was wrong, reconnected the Cat5e cables back, which were still fairly new, and speedtest.net tests went right back down to 9-10Mb/sec on downloads.
All because I wanted to upgrade my cables to match each other in color, I didn't expect anything more, just ran the tests out of being curious. And if TWC (the ISP) has an appointment, will switch those cables right back, so that they can't 'tune' their speed to my cables that were a grand fortune of $18 shipped (6 cables).
Now I've had to purchase a couple more since, though on some computers (notebooks) just run wireless & disable the Ethernet port, because it's inconvenient to connect/disconnect cables & sooner or later the port will be broken. My router is fast enough to give the same fast speeds anyway.
While some may have never heard of Cat7, it's one that's thicker (too short & impossible to work with), basically with the same signal properties of Cat6, yet has more insulation to prevent interference from microwave & other very strong signals. The only other place I've seen these used is in the hospital, when going an ultrasound. For me, it's to ensure a really great connections between the modem & router, and router to VoIP device, where obviously the less interference to include background noise, the better.
I think in the next week or two, will go to Earthlink Extreme (100Mb/sec) for $10 more, yet as above, will have my 5e cables plugged in when making the switch in speed. That is TWC's standard & still comes with new routers & modems as well. Don't know why they want to stick with dinosaur cabling, because it does go back to being the 'weak link' in the supply chain. Maybe for residential customers, it's what the ISP wants.
Whatever, do not pull out a set of these & ask to connect to these when the ISP is performing setup, you'll lose speed that you're paying for. This is because they measure performance on 5e cables, and will 'tune' the speed back to 5e performance. I merely posted the cable upgrade as a 'hidden' upgrade that works for many, though not all cable Internet subscribers. It doesn't work on AT&T & ISP's based on fiber optic or other phone lines, I've tried three times for other, no difference. Yet around 8 out of every 10 times, the speed will jump noticeably for those with cable Internet, for one person, from 100Mb/sec to 145Mb/sec, and that's a massive upgrade (actually a tier above) for the cost of a cable. Even the upload jumped to match, though he has his own Motorola router, and installed a heatsink in the place where the case was made for one, but Motorola didn't install it, and this was over a $150 modem at the time (maybe 3 years back). Pricing has dropped since then & have my eyes on a $100 model that has 16x4 download/upload channels & 2 year warranty. If I were to stash that $10 modem fee for a year (which I would), could order another w/overnight shipping for the cash saved.
This modem, if one could do it legally, provide 100Mbps (download) to over 6 homes, nearly 7. It'll surely futureproof my network for a long time.
So my point is that for many customers, the quality & rating of the cables used are everything.