Only thing worth changing imo is tyres,chainring guard, and shorter cage mech.
I tend to upgrade brake blocks and cables as a matter of course on folders.
Get rid of the chain catcher if fitted by installing,paffic chain tensioner near bottom bracket as mk 4 come with standard. To avoid the catcher getting jammed in cassette. Expensive if happens. I had to buy new rear mech.
Hence I dont run the chain catcher anymore on my birdies. Its not an issue on an IHG bike.
Else prefference for saddles,grips and peddles as usual.