That's not how you asses performance at all. Maybe you can saturate the NVMe link with AES in idea circumstances, but you may be killing memory mapping and churning I$.
To say anything interesting about performance on these modern machines, you would have to benchmark some real workload.
Speaking of which, software that doesn’t use the AES-NI instructions is becoming glaringly obvious because the performance difference is so huge.
In the era of mechanical drives and 2 Mbps “broadband” nobody would notice. Now with SSDs and gigabit home internet, people do notice but vendors are still pretending they can just ignore the need to offload encryption.
VPN products and IPsec especially is almost always a disaster in my experience.
When evaluating any kind of network security product like a virtual WAN appliance, tunnel, or whatever, check the throughput. If it can get tens of gigabits for a single stream then it is using some sort of offload. If it seems to hit the wall at around 1.5 Gbps per core, do not buy.
How much does this affect other processes happening at the same time? If I'm playing an open world game that streams the environment off the ssd, how much is this going to contend with my cpu issuing draw calls, doing physics calculations, etc.
I run FDE on all my machines, encryption and sector sizes are aligned, I can still do a 3000MB/s IO no problem. Doesn't affect anything I'm running, even databases like Postgres.
The penalty is not huge especially compared to fully software implementations but it's not zero. And it takes memory bandwidth too.
I don't use FDE on my gaming system for this reason. It's a big heavy PC that never leaves my house with not really any personal data anyway.