Sorry, never saw this to respond
Yes, I ve been on a Viking river cruise.Not one of the new longships,but older with only french(like a big window)balcony.The newer one now have a SMALL regular balcony.It s MUCH SMALLER than on ocean ships.Ships must go thru locks and that determines width.
Have been on 10 river cruises and Viking was not my favorite,prefer AMA,Uniworld,Scenic, or Avalon.Just a little step up in terms of cabin,service,food,excursions,etc.
Do a lot of research on ea.website to see EXACTLY what cabin and balcony looks like.
Any specific questions, will TRY to help.