This page of the guide to Death Stranding answers two questions - are there any important choices that could affect the course of the main campaign, and does Death Stranding have the option to romance the NPCs.
Important choices in Death Stranding
Some scenes in Death Stranding (especially those from the thirteenth chapter) suggest that there are choices and that decisions made may have different consequences. However, this is a misconception because there are no important choices in Death Stranding - the game's plot has a linear course leading to only one possible ending.
It is worth noting that you can skip some orders for Sam. However, this isn't the result of the campaign's nonlinearity - you can ignore only minor orders that aren't important in terms of the main plot. Fortunately, even if you miss these orders, this won't have any impact on the game's finale.
Romances in Death Stranding
There aren't any romances in Death Stranding, nor sex scenes, although there are moments in the game where the characters are naked or appear in their underwear. This, however, never has typical sexual overtones.
The main character gets new friends, e.g. Fragile, but these two never enter an intimate relationship. As for the topic of making more personal relationships, Hideo Kojima went even one step further. Sam Porter has a phobia due to which he avoids direct physical contact, even obvious reactions like hugging or shaking someone's hand.