Expanding the storage for your Mac with a DIY external drive with NVME SSD isn’t simple. To get maximum speed from modern Macs with Thunderbolt ports mean getting a Thunderbolt enclosure. These are the ones that seem to play well with Macs: ACASIS model TBU405 and Orico model M234C3. Here’s a table showing which chipsets are the fastest for these enclosures: dancharblog.wordpress.com/2024/01/01/list-of-ssd-enclosure-chipsets-2022
These NVME models have the least reports of issues: Western Digital Black SN850X and SN850 and Most Western Digital drives.
And Samsung drives 970 and 980 series are the ones to avoid because of compatibility issues with the TRIM command of macOS Monterey and newer versions. The incompatibility causes very long mount times of five plus minutes after the drive has been used for awhile.
It’s surprising that this information isn’t more widely known, but it’s probably because DIY External SSDs are not that widely used.
With a Thunderbolt 3 enclosure you should attain the speeds shown in the image below with a modern MacBook Pro
