Camping sleeping mats

Not necessarily. A thick air chamber may be comfortable without providing much insulation. Compare the stated R-value for the exact size and construction.

A clean, smooth pitch protects the fabric. A suitable ground sheet may help on rough ground, but remove sharp stones and twigs before lying down.

Yes, for example foam beneath an air mat. Check that both stay in place and fit the tent. This also increases the packed size and weight of your sleep system.

Clean and dry, following its instructions. Self-inflating mats are often stored with the valve open; air mats may have different requirements. Never roll up damp fabric for storage.