When driving along the grill mesh bit will always rattle in the tray so use a silicone mat to stop it, The thin baking sheet type are ideal and are also heat proof so are safer than stuffing the grill with something potentially flammable in case you forget to take it out when you light the dam thing.
Line your cupboards with a layer of foam (we cut up some camping mats) then put a piece of matting from Ikea on top, The foam deaden the sounds and the matting keeps things from sliding around.
Put sticky back velcro (the fluffy side) between things that rub like timber parts or dashboards or curtains (the plasticky type).
Stack your plates vertically and not horizontally to stop then rattling as much.
Car sponges are great for stashing in between things that may move.
A couple of weeks ago we started getting a squeak noise whilst travelling. The culprit was the dam mosquito screen that fits to the vans habitation door (the main door). They have a foam surround on the edge of the frame and it’s started to break down a little and is now chaffing on the doors rubber seal. Phillips screwdriver out and 10 minutes later so was the dam frame. I have just cleaned it up a little and retightened the fittings so hopefully it works until we get back at which point i’ll change the foam section for something else. I have now quite a growing list of things to correct, fix or change when we get home.