The same object can be affected differently by different formats. A little, handmade candle could sit quite happily in a box, sit quite messily in a paper bag, or be difficult to handle if it is only covered in thin paper and the lid has sharp corners. A soft, knitted scarf might not need a carton but will certainly need tidying in its fold, in the tightness of its closure, or in a paper band or tag. Picking a format is about more than just the most beautiful choice; it is a question of object, geometry, mass, fragility, and function.
A box offers support for objects that need a frame. Corrugated boxes and cartons give form to objects that must not be crushed, bent, or directly pressed. They give space for labeling, and they allow cushioning to be applied evenly, with a good base, sides, and top. The trap here is a box that is too big. An oversized box leaves the paper filler to take over as the saving grace of structure, and uncontrolled object movement.
A mailer is well suited to flatter objects or those that are already relatively sturdy: small stationery, prints with board backing, folded fabric, and small light objects with simple shapes. Paper mailers or padded mailers can be a neat, straightforward choice, but can be risky on objects with fragile corners or edges, raised details, or shapes where space is needed around the object, and may be too tight. Ensure that the object can easily slide in (without being forced into the opening) and that the closure flap can be shut (without being distorted around the object).
A bag can be a good option where there is an emphasis on presentation and where the object can stand safely or lie safely. It is a common option for gift items, light-weight items, and items that already have some internal wrapping. The challenge is in the uncontrolled movements. A bag can look tidy externally while its contents are moving, tilting or rotating inside, and rubbing up against the sides. Tissue paper or a small insert may be able to fill a gap at the bottom, or to give a stable base, but there is no amount of tissue at the top to cover a loose fit at the base.
Paper wrap can be appropriate where the object has a shape that wraps around well, and does not require a more protective structure. Wrapping paper, kraft paper or tissue can be a neat finishing surface, but are more dependent on measurement and allowance. Objects with sharp corners, with raised handles, or unusual shapes can result in torn or wrinkled paper, or bulky folds. Fragile objects may need to be part of an outer, layered, protection, and not only wrapped in paper.
Consider the structure before you think about the final materials. Place the object on the table. Decide what your structure needs to achieve (a form, containment, a finished gift surface, protection of a surface, space for labeling). Next, test your choice with a piece of scrap or empty carton or sample bag. A tilt check will show if the object shifts too much. A closing check will show if the flap/seam/fold is being stressed by the object.
The best structure will have fewest structural problems. If the object is already solid enough, a wrap, mailer or bag can be fine. If the object is fragile, uneven, heavy, or potentially moving, a carton with planned padding is a more suitable exercise. Choose an approach that will allow the object to remain calm, will enable a neat closure, and will pass your finish-line check across its top, side, base, seam, and opening-edge.