Will Carbon Copy Cloner (CCC) file/rsync-based clones to a "target disk mode" T2 MacBook work?
I cloned my old Mac Mini 2012 onto my new 2018 Mini (with a T2). 
Trying to remember exactly how I did it (in terms of what volume booted and how they were connected) but there are two important points:


After cloning, the OS would not boot, and I had to reinstall the OS on top of newly cloned disk. (Keeping all my data, apps and settings.)
The Admin user on the disk does not have a 'Secure Token', and can't be used to change Secure Boot settings. Follow Peter Thorn's excellent answer in this question. 


I've previously cloned a succession of my Macs over the last 15 years or so, and never had a problem before.