They literally pack as presented. So I would recommend getting organised.
If you've left your wellies/slippers by the backdoor in say your kitchen, they may well be in a box with your saucepans or airfryer, but the box will probably be labelled kitchen pans.
Roll forward to moving in day or in your new house and you want/need your wellies/slippers....good luck finding them.
Maybe above isn't the best example but after 11 house moves with the packing service I highly recommend a big organisation of drawers/cupboards and rooms. So items are in a box labelled to the room you would expect to find it. They do label boxes but not with EVERY single item.
Any items you don't want packed ideally need to be completely separated because a team come in and pack on auto pilot, they pack fast and well. Things like hoover/cleaning items you may need for arrival at your new property, bedding/air bed overnight bag,car keys, handbag,shoes, mugs and kettle (although they will ask about kettle cos they'll want a cuppa or 2) ideally need to be put in an out of bounds area. I would typically use the car or one of the kids bedroom - having already moved one kids stuff out into thier brother or sisters room.
Empty bins, dishwasher etc or else it gets packed with whatever is inside.
To speed up we would unwire/disconnect any items connected up (not much these days) but back in the day we would disconnect sound bar from TV/sky box etc. And tape remotes to the TV or whatever. One move we think we threw out a remote in error with the packing paper whilst unpacking.
We sometimes would disassemble some furniture (although when you have your survey you can discuss this) Typically this would be beds and just sleep on our mattress on the floor. Also, play equipment in the garden we would disassemble because typically the garden and out buildings are last to be packed in the van and this time of year it gets dark 4pm onwards. I always used takeaway containers or ziplock freezer bags for any screws/bolts/Alan keys and label clearly with a sharpie and again tape it to the item disassembled so I knew exactly what I was looking for the other end. They will disassembled for you but we would sometimes do it if we were moving several hours away, to help speed up packing so we could head off asap.
They wont pack chemicals, paint or flammable, but they'll explain this in your remove survey.