The TC works well handheld. Some people use the XT handheld although I don’t find this ideal.
The Factum could be used handheld, but it is too big for me and the grip that they make for it is a bit too thin to be comfortable.
The Rm3Di has a grip which makes it useable handheld, but I find only with two hands, its too heavy.
The best cameras handheld for backs are:
Alpa TC
P1 XC
Alpa SWA (dual grip is perfect handheld)
P1 XT - less grip than the SWA
In a way the only shiftable handheld camera in my view is the SWA, followed by the XT.
TC is the best.
Alpa make three grips: a small thumb grip (which is useless), the small one for the TC (really good, can have a leather strap) and the ergo grip; the ergo grip is similar to the one on the TC:
The big cameras Max, Plus, Rm3Di etc. are too heavy to be used handheld - the grip is mostly for setup and handling.
In fact, before the TC was released the Alpa SWA was conceived as a handheld analog camera incl. a viewfinder accessory with its two grip functioning as a stabilizing design.