Campaign
Death means losing carried items and respawning at your outpost, then continuing, according to the developer. Corpse recovery, autosaves and what counts as carried are not explained in the reviewed text.
Survival
The developer states that death is final and the world resets to zero. Difficulty settings and exceptions have not been verified.
Which mode to choose
Editorial suggestion: Campaign suits learning with a less severe player-death penalty; Survival suits players who want the announced world-reset challenge. This recommendation is not based on hands-on play.
NPC death is separate
The community description says recruited survivors do not return after death. It does not describe an NPC exception for Campaign. Player respawning should not be assumed to apply to companions.
Before committing
Check the released mode-selection screen and save rules before investing in a long-running settlement.