Having played PUBG a fair bit now, Fortnite Battle Royale is a remarkably accurate copy. The main thing it is missing is vehicles which is kind of a severe omission. There’s less opportunity to frenetically outrun the blue zone without vehicles, and the insane loud vehicle driveby attraction aspect.
As for the mobile cover vehicles offered, that’s no problem; you have standard Fortnite building and that works perfectly. Caught in a field? Just build where you stand; you’ll have enough for at least 4 reasonable walls even with the basic stuff you pick up as you run around.
The grenade launchers and rockets have a whole 'nother meaning in this mode since they DO blow up all structures and are fantastic for flushing people out of any kind of building. Way different than PUBG in that regard, where camping in buildings is hard to deal with.
edit: it is also missing random airplane crate drops but those are so infrequently accessible to me that I often forget they exist. Apparently they’re adding them soon.