Boards are stencil pasted before part placement. the paste indeed will hold parts in place which is why I'd rather move the board around than the PnP head.

Large items that there are not many of I would still put on by hand. I'm trying to speed up the fiddly small parts that there are lots of and not try to do the easy big ones that would be near impossible to pick up and move like large electrolytic's as I can put them on faster by hand anyway