Even though I have increased the touchpad speed to the highest level in BTT, its speed remains slow. How can I speed it up even more?
unfortunately BTT can not do that (on modern macOS versions) 
The best app I know in this category is CursorSense. The fourth most important app on my mac ... after BTT, of course 
unfortunately I think on macOS Sequoia Apple disabled the API CursorSense was using... so enjoy while it lasts 
Really? Mm, a good reason not to update.
Couldn't you find a way to do that? Would be great!
And wasn't there once a terminal command to accomplish more or less the same thing?
yes first it worked with a terminal command, Apple killed that at some point. Then BTT also had this included once. Then Apple killed the API. Cursor sense was using a more low level approach - I was also looking into that as well, but now it's probably not worth it anymore as Apple has locked it down too ;-(
Not sure why they don't want us to change that stuff.
Apple also does not want fn to be used as a modifier (for whatever reason). Nevertheless, it works very well with BTT. Little things like that have never stopped you before. If you want, you “ll find a way”. I have full confidence in you. 
I'll keep looking, unfortunately this stuff gets harder with every macOS version.
They work harder, you work smarter.
Seriously, this trackpad is too slow for many. Maybe Apple has finally understood this and offers a higher speed as standard with Sequoia. Do you happen to know if that's the case?
If not, you are the last hope of all Mac users.
no the maximum allowed speed hasn't changed ;-(
Grrrrrr! Completely incomprehensible.