Know which construction you are choosing
A liner is a removable inner sock. A liner-plus-hiker set supplies two separate pieces, while a double-layer sock joins two fabric layers into one product. Toe sleeves are another feature and can appear on either a liner or a standalone trail sock.
Check room for both layers
Put the liner on, position each toe and heel, add the outer and then try the complete system in the intended footwear. If the shoe already feels tight, adding a layer is not a useful shortcut. Check for folds and unwanted bunching before leaving home.
Read both material labels
The Injinji Liner + Hiker example contains a synthetic liner and a wool/acrylic outer. The complete system is therefore not wool-free. Injinji also lists a separate merino liner that it says can be worn alone or beneath an outer sock.
Plan washing and drying separately
A removable liner and outer can be washed and rotated independently if their care instructions allow it. That is a planning choice, not proof of a particular drying time. Enter your own drying assumption in the trip planner and account for each piece you carry.
Keep performance expectations realistic
Manufacturer claims about friction, moisture or blisters do not establish how an exact liner will feel in your shoes. Choose a construction you are willing to fit and manage, then try it before depending on it for a long trip.