Luke, thanks a lot for such a high appreciation of my modest work))
Now, concerning your question.
According to the corresponding Regulation of 1947, cuff insignia were allowed to Riverine Fleet officers only, first of all, to the operational ship stuff. But they had shoulder straps as well.
Officers of all other Riverine services used shoulder straps only (according to regulations), but as it always appears in the life some of them neglected these Regulations and wore cuff insignia as well (because of their decorative appearance).
Officers shoulder straps resembled military ones, but stars were situated longitudinally in a manner of the Russian Imperial civil officers.
Enlisted and NCOs never had cuff insignias in this period of time, and they wore shoulder straps only - narrow with transverse silver or gold stripes as their ranks indication.
The picture of a uniformed lady in your message demonstrates the rank of a Captain (or Engineer Captain) 3rd Class, which is equivalent to army Major or Naval Lt Commander. There are two indications of this rank: shoulder straps with "rails" and one star (btw, there is a slang expression in Russian "получить рельсы" - "to gain rails", meaning to get a rank of a Major (Lt Colonel or Colonel). As you can guess, "rails" mean these two parallel longitudinal stripes on shoulder straps)) and cuff insignia with three MEDIUM (not NARROW) stripes. Actually, there were three stripe sizes for cuff insignia: narrow - 6 mm, medium - 13 mm and wide - 28 mm. The only rank with narrow (6 mm) stripes was a rank of a Junior Lieutenant (Technician Junior Lieutenant), who wore 4 narrow stripes. Before as the 1947 Regulations were approved, there were several variants of cuff insignias, but none of them contemplated cuff insignia for enlisted and NCOs. Therefore, the lowest officer's rank of a Junior Lieutenant meant 4 narrow stripes, and all other ranks used medium and wide stripes solely.
aka Dorward and Dmitry Belokurov