Minecraft wiki entry for Nether_survival, associated text: Nether Fortress: While this is a lucky place to spawn, you must protect the portal well. Make sure the ceiling is 2 blocks high to avoid having wither skeletons spawn there. Make sure to light it up well, as blazes can spawn at higher light levels than most hostile mobs, and they send out alarm calls when attacked. However, you have immediate access to what most players come to the Nether for: blaze rods and wither skeleton skulls, as well as naturally-generated fortress loot.
Bastion Remnant: While slightly less lucky a spawn, you have access to magma cube spawners and a partly laid-out base. Watch out for piglin brutes: they aren't fooled by gold armor, have high health and powerful attacks. Piglins attack you if you attack a brute. See Tutorials/Defeating a bastion remnant to learn how to get the large quantities of gold blocks that it contains.