Both those pics above are of Stahl models, 1st excavator, 2nd dozer, to show you the internals.
I see you mention you had researched the 4200, I've made some comments on this forum & others... none of it good news... I got one of the 1st ones just to satisfy my curiosity & the hyds/electronics were junk right out of box.. I didn't get much run time before it quit - permanently!
I'm gonna use Leimbach hyds & other electrical to get it working well again soon.
I like the Spektrum DX18 specifically for excavators, mainly b/c of the rotary proportional slider on each side of the radio to operate the tracks. You use the AR8000 rx which is good up to 9chs, then another device that plugs into the rx called X-Plus gives you the other 9chs... I haven't gone beyond needing 9chs.
It has 50 model memory, tx binds with all the other smaller ch rx's (maybe not the DX5
) so you don't need to buy the more expensive AR8000 rx if you're only needing 6chs or less on other models.