AOMEI Backupper Pro 661 works in Win11, though I only tested basic disk backup & recovery. The WinPE version, by default in C:\Program Files (x86)\ AOMEI\ AOMEI Backupper\ 6.6.1\ Winpe64\ , will run in Windows, though it needed to be registered/activated separately, and it did run in a VM with Backupper not installed, so it may work as a portable version -- I say *may* because in the Tools section it says you need to upgrade to get the portable version, so the WinPE version may or may not work consistently with different devices &/or copies of Windows. Backupper adds a service which runs with Windows, & that opens 3 listening online connections with AOMEI servers -- when you run the app you have 3 more connections communicating with AOMEI.
Installing AOMEI Backupper Pro adds the program's folder, a new folder in ProgramData, the following files in C:\Windows\ System32\ : ambakdrv.sys, ammntdrv.sys, amwrtdrv.sys, winsevr.dat, plus C:\SYSTAG.BIN. When I monitored the install in a VM, the registry picked up 218 new entries.
While AOMEI Backupper Pro works, I've only got it installed in a couple of VMs, & have only used it a few times since around 2013 - 2014 when it was on GOTD [there have been updates since then], so I can't fairly say if it's great, or not. Back then I had bought a tablet with 32-bit UEFI BIOS, which AOMEI's bootable USB sticks would not work with, but Macrium Reflect would, so I started using that on all of our devices, and have had no reason to switch everything over to something else.