Go shoot it and don't worry. Most of the useful stuff that will fit an 870 will fit the NEF too (Sidesaddles, light mounts etc). I got one just to see how good they were, of course it'll be 20 or 30 years before I really know if it''s as good as an 870, but...
So far so good, it's even a touch heavier feeling than an 870, but its action has smoothed out nicely. All the controls are in familiar places, since I'm used to 870s. I like mine, I put a 4-round Sidesaddle on it but you can put a short LE type forearm on it from an 870 set and it'll work with a 6-round Sidesaddle. It has a carrying strap on QD awivels and a white light (TLR-3 LED on a Streamlight 69903 mag tube mount, there's room between the front of the forearm and the barrel ring for it).
Again- go shoot it- LOTS! Software is more important than hardware.
Mindset - Skillset - Toolset. In that order!
Attitude and skill will get you through times of no gear, better than gear will get you through times of no attitude and no skill.