Snibby
all Pixel devices got a nice upgrade from kernel 5.10/5.15 to kernel 6.1.
9th generation Pixels were already on the 6.1 LTS branch.
Are there any distinct improvements that this upgrade brought us?
Some minor security, performance, battery life and other improvements along with more bug fixes which weren't backported. Also, new bugs added in newer Linux kernel versions which didn't get fixed via backports. Whether there are more or fewer bugs in the small subset of code that's used for 6.1 compared to 5.10/5.15 is unknown and we wouldn't even try to make a guess.
Does this mean that NTFS formatted USB-C OTG drives are now supported on Pixels with read/write functionality? Or would there be something blocking this?
No, only FAT32 and exFAT are supported for external drives for security and simplicity reasons. NTFS and *nix filesystems are not reasonable portable storage formats due to having all kinds of non-portable metadata and are overly complex. They have far too much attack surface for this purpose. It would be reasonable to use a special implementation written in a memory safe language like Rust within a userspace process but that doesn't exist. exFAT is the normal filesystem for this purpose. You can use an app directly using the USB device for other filesystems.
That kernel NTFS implementation you're talking about is full of serious bugs including data corruption and memory corruption bugs. It isn't very robust yet and it's not going to be a good idea to use it with untrusted data in the foreseeable future. Android has verified boot and therefore any filesystem it uses for writable data is untrusted, which means f2fs for the internal data is already a big open issue in this regard, but ext4 would be too.