you can choose Apple virtualisation in UTM instead of QEMU too. Apple virtualization is optimized for M1+

That's a bit like saying "instead of ext4 you can use an SSD" in that the things involved span multiple layers. When you select the option to use Apple virtualization framework in UTM you're still using QEMU, what you're changing is the backend QEMU is using for the CPU virtualization.

QEMU has a Hypervisor[0] backend these days, called “hvf”.

https://wiki.qemu.org/Features/HVF

[0] “Hypervisor” is a “sibling” to the Virtualization framework. IMHO, the naming is incredibly confusing (: