I am planning to get an external storage for Ventoy use. My current random usb 3.1 stick writes .iso-files with only 10-15 mbps only. I found this webpage for usb stick speed comparison: https://ssd-tester.de/usb_stick_test.php
The fastest usb sticks writes 800-1000 mbps in the crystaldisk-test.
If you have personal experience on this, please recommend which approach is better.
Curious, do you have examples of those high end flash drives?
My particular testing was with an SSK SD300, which is roughly 500MB/s up and down. I have benchmarked this and confirmed it meets its rating.
I have thought about buying something like a Team Group C212 or Team Group Spark LED, which are rated at 1000MB/s. The 256GB version of the C212 is available on places like Newegg and Amazon for around $27 USD at time of writing, but they make variants as high as 1TB.