I think it is quite hard to touch type and to not also bottom out when touch typing. There are notable keyboards such as Topre based keyboards makes it hard for one type and actuate without having to press it so that it would feel like as if one has definitely sent the key press and that the machine has recognised the input. From the actuation point onwards to when one hits the bottom of Topre board it is very soft and therefore very quick to hit the bottom. Even for my APC membrane board which seems to actuate somewhere close to around halfway or top but because it feels stiff (on certain keys) I have to press harder so that it feels like as if the keys have been properly actuated but at the same time I bottom out.
Touch typing, as broadly defined is when one types without looking at the keys, not to type and to not bottom out. There are certain keyboard switches which may seem to make it easy for one to actuate a key press and to not bottom out but there are others which makes typing without bottoming out very hard (almost to the point of literally impossible). Therefore to touch type and to not bottom out would probably make one formidable at that keyboard and/or that particular switch. When it comes to switching keyboards and/or switches, well a different learning curve ensues.
Frankly speaking, the touch typing term as wikipedia states I would agree. Even the age old typing tutor softwares, they all seem to enforce the same set of theme, to use all 10 fingers (or eight fingers and two thumbs) and to type efficiently without 'hunt and peck' sort of style. I personally have not found a single touch typing tutor that would also gauge if one would bottom out the keys or not when it comes to touch typing as that would be very pedantic in my sense. Granted to touch type and to not bottom out is far better if one wants to achieve even more faster speeds but really, the whole premise of touch typing was to really use as much fingers as possible without looking at the keyboard.
Switching between various keyboards I have here, it is virtually impossible for me to master touch typing and typing without bottoming out on every keyboard and their specific key switch. However what is true is that at least I have maintained typing without looking at the keys all that much. I mean apart from the fact that my keyboards all have various layouts (ANSI, JIS, big-ass enter and soon ISO) so it is not easy for me to memorise all the keys and their specific layouts as well as to type on all of them without bottoming out.
ErgoDox would be killing two birds with one stone. I have no qualms with you choosing ErgoDox or virtually any ergonomic mechanical keyboard for that matter however I must stress that if it is your first time dealing with mechanical keyboard, it is ideal to not try and kill as many birds with one stone. As I said before, if you bought ergonomic mechanical keyboard for instance but you find the layout a bit cumbersome to make use of, you may not only ruin your own perception of what ergonomic keyboard is capable of but also to ruin your experience with mechanical keyboards as a result of finding ergonomic keyboards too daunting.
There are many styles as to what one can take as being ergonomical keyboard. You have ErgoDox, you have DataHand, you have BAT keyboard, you have Maltron keyboard, heck you even have AlphaGrip (which doesn't even look like your average keyboard). No not all of those keyboards are necessarily mechanical, most of them are chorded and are also ergonomic. They can greatly vary your experience with typing in ergonomic sort of sense but you may also find as a result of not only because of using them you may not be able to live easily without them.
