Here is the article Losing the Apple storage tax on M1 Macs | ZDNet
The author talks about Thunderbolt ports: sure these are fast, but did you searched for an external enclosure: they transfer money out of your pocket faster than they transfer data ! M2 storage is quite fast.
But there are two drawbacks:
What are you 2¢ or 2$ ?
There are two things: the speed of your external and the stability of your connection.
I've tested external fast drives for transfer speeds and they are excellent. A fast connection doesn't speed up a slow drive.
The gotcha for any external drive is the connection. In my experience the USB-C connector is the most unreliable connection possible. It is small, short, and has very round corners. It is extremely easy to bump the cable and lose connection.
I've lost the contents of a 250GB SSB because of this and was very unhappy. (yes I had recent backups).
My hot take is external connections are for devices that don't care if the transfer drops.
hmm... the author talks about Thunderbolt ports but the external enclosures are USB 3.1 and USB 3.2, so there are faster opportunities for external drives.
I run my main MacMini 2018 from an external drive (i-Tec enclosure, WD Black 750 NVMe ) at 2000MBit read/2500MBit write which at least is OK. Costs: 280,-EUR. Making an external Thunderbolt drive bootable is a bit of a hassle but can be done.
The Minis internal 512GB drive is slightly different in speed at 1900/2700 read/write.
Upgrade from 512 to 1024GB disk capacity is 230,- EUR
Upgrade from 512 to 2048GB disk capacity is 690,- EUR
2048 GB NVMe SSD would cost about 300,-EUR plus 100-150,-EUR for an enclosure
And of course there are preinstalled or ready-to-go external Thunderbolt 3 drives like the Samsung X5 which runs at 2100/2500 read/write.
1024 GB are about 350,- EUR
2024 GB cost 500,- EUR
The M1 MacMini with the 512GB internal Drive runs at 2900/2900 read/write
Upgrade from 512 to 1024GB disk capacity is 230,- EUR
Upgrade from 512 to 2048GB disk capacity is 690,- EUR
all prices are from the german Apple Store and Amazon Germany, so they may differ in other countries and from other resellers.
My take is: with real Thunderbolt 3 chipsets and enclosures speed on external drives connected to recent Macs is on almost the same level the internal drives have. For big installations with vitual machines etc. I would buy a bigger internal drive, for gaining extra storage a fast external drive would be my choice espacially beyond the 1024 GB limit.
2 cents for a weekend read 
[edit]
be sure to test external drives under production conditions: write speed can slow down when docking stations for port replications are set in between. For example CalDigits T3 Thunderbolt 3 docking station cuts the Samsung X5 speed down to 1200/2400 write/read.
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