Laugh, perhaps "down under" PCs are 10 years behind in their technology and/or your brick-n-mortar PCs are bargain-bin (i.e. very inexpensive [cheap] models).
Seriously, though, low price PCs (or laptops) really do cut corners on hardware, which very much can create the problems you note.
(Although there are some "gotchas" that can trip you up. For example, I recall, it used to be [still?] on Windows PCs running Microsoft's CTCP, their servers ran with different performance defaults then their "workstations", although I also recall you could manually enable the extra performance settings on "workstations" too. Oh, and BTW, these were settings often needed for pushing a high transfer rate. [Note my mention of RWIN sizing, for TCP, in my first posting.] Of course, if PC management folk, discover you can actually obtain a much higher sustained transfer rate, changing some network options on the host, and do so, it can have some "interesting" network repercussions.)
Conversely, you might find if you run one of the better Linux distros on the same hardware, it doesn't seem to have the same network performance high throughput issue.
Yea, currently, a NIC supporting more than gig would be expensive, but then I remember when at one company, they were still buying TR 4/16 Mbps NICs, that cost as much, if not slightly more, as the PC which had an on-board 10/100 Ethernet NIC. (NB: because of this, they decided to move from TR, running at 4 Mbps, to Ethernet running at 10 Mbps. [I convinced my department to be the very last of this conversion. Why? Did I mention, the 10 Mbps Ethernet was on large chassis hubs? We converted to Ethernet when they replaced the hubs with large chassis switches, still 10 Mbps.])
So, I very much expect like other PC hardware, eventually newer PCs will come with faster than gig NICs, standard. (They sure have come a long way from my first personal microcomputer [IBM PCs didn't come along until a couple of years later] or the early dumb terminals I used at work [which were much nicer than punched cards]).
But you're correct, a typical office PC, today, doesn't come with a 10g interface, let alone 100g.
However, OP seems to understand these issues, because of their mention of NVMe and obtaining 9.6 Gbps on a 10g NIC.
I believe they understand a 100g NIC can easily stress almost any "PC", but if you read up on the 100g NICs, different vendors try to mitigate the impact to the PC itself. The "gotcha" here is whether a vendor's 100g really works (well), which, I suspect, is why they are looking for recommendations.
