Since my Ipad broke down, I have been having a VERY hard time building. It's become a sort of an experiment on how far my patience can be. :)
2 things that make it extremely difficult when building on android/PC is:
1. When Items are overlapped, you cannot mine the smaller object inside a bigger one, until you mine the larger object first (a block in the space a bridge takes up for example)
2. can't use butler bots - moving liquids, removing backdrop and placing lamps on air is off limits.
And one small issue:
3. on Android when you place an item, the bottom left corner of the item is placed where you click, while on ipad and PC where you click, the large objects are centered to that area. I already got used to this, but everytime I switch a device, it takes time to reformat my brain :))))
I am sure long-term PC builders have lots more to add, but these are the key things I noticed in the past few weeks.