Attention: The current information (April 2025) from Galaxus in the model selection fields under the title Height (61cm or 65cm) is total rubbish. 61cm is actually the width of the assembled Concept2 RowErg and applies to both the standard and the tall version and has nothing to do with the seat height. Nobody knows what the 65cm are supposed to mean... so if Galaxus thinks that these are the height specifications for the versions, that's wrong and would be the wrong way round. According to Galaxus, the Tall version would be lower at 61cm than the Standard version at 65cm.
On the Concepts2 homepage, the manufacturer writes: "Our standard RowErg has a seat height of 36cm, while our raised version has higher legs that offer a seat height of 51cm. The raised version is a good choice if you appreciate the comfort and appearance of a taller unit. The raised seat height can also make it easier to get on and off."
The higher version is therefore not necessarily intended by the manufacturer for taller people.
The lower seat height of the standard version works just as well for tall people as it does for me at 173cm tall. A colleague of mine is 189cm tall and has no problems whatsoever with my standard version of the Concept2 RowErg, so you won't be "standing" anywhere while rowing.
The length of the running rail/monorail would be the limiting factor for significantly taller people. However, this is the same length for both versions on sale. Quote from the manufacturer: "Users with an inside leg length of more than 96.5cm may need an extra long monorail. Please contact us for further information." I think the standard length of the monorail is easily sufficient for a body height of 194cm... even if I don't know the corresponding inside leg length of course.
Once again about the seat height. If you want to keep the option open to add slides and/or FlowRow boards (both not available on Galaxus) to your Concept2 at a later date, I would definitely favour the lower seat height of the standard version. Otherwise the overall structure will be too high and too unstable.

I am 174 tall :) .... the height doesn't matter ... only if you wanted to ride "higher"
for me the "standard" height seems to be more stable + cheaper ... why not