They fixed Sackboys stuttering in like a week, though I dont know if that game is unreal engine, but it'll probably get sorted out. Sony has a dedicated PC porting studio so it should be alright. Although literally nobody played Sackboy so who cares.
Sackboy is a UE4 game. Unfortunately this isn't a port by Nixxes, it's from Climax Studios who I have never heard of until now. You're right though, if it's a problem it will most likely be fixed by the time I play it. I'm sure this will launch at the same price as Spider-Man/Sackboy/Last of Us and I will be waiting a year to buy it.
I just noticed the minimum and recommended specs have been posted on the Steam page. The main thing that stands out is the RAM requirement, with the minimum being 16 GB and 32GB being recommended. The rest seems to line up with other current gen games with minimum spec being an i5 6400 or 1500X with a 1060 or RX 580 and recommended being an i7 8700 or 2700X with a 2070 Super or 6700 XT. An SSD is recommended, but not required. It will be interesting to see how it runs on a hard drive.