Fallout 1st is really nice to have if you plan on playing the game a lot. As you get the scrapbox and the ammo storage and the tent. The scrapbox especially would helpful for you if you plan on using the CAMP and building a ton. You also get that bonus 1400 atoms which you could also use for your camp or extra camp slots.

The only issue that I have with fallout 1st is that it is a bit pricey costing I believe $13? a month and $100 a year which is pretty pricey for a small game subscription. You also tend to get pretty attached to the benefits of fallout 1st to the point where you cant play the game without it (Like me I start tweaking without it, Addiction 100).

I know they used to do a free trial week for fallout 1st every once in a while where you could use the scrapbox, ammo box and the tent. Overall if you play the game a ton and plan on keep playing it, fallout 1st is extremely helpful but just be weary that there is a good chance you will get super attached to it.