hi there before jumping to pix insight you may want to give Startools a go. I find it does a great job and is simple to use but can also be taken to a next level...maybe not quite the next level of pixinsight power but far enough for me :-)
Wondering why 20 min subs? With the ASI533 and your scope at it's focal length I think you would be far better off with much shorter exposures that will be less affected by tracking, seeing etc. I've had good results on this object with 2 min exposures using essentially the same sensor type latest liked below processed in Startools. Certainly I think you would see better results with 20 x 5min as opposed to 5 x 20min as here.
https://www.astrobin.com/full/qovqep/0/