Minecraft wiki entry for Nether_survival, associated text: Crimson Forest: Watch out for hoglins, because they deal high damage and high knockback, and can fling you into the air. However, like pigs, they drop porkchops when killed. Piglins are formidable enemies that frequently spawn here, and they attack players who are not wearing gold. They also become hostile toward those who open chests, ender chests, barrels or other containers, or destroy gold-related items like blocks of gold, ores or gilded blackstone. These mobs barter, so from them you can get crying obsidian and potions of Fire Resistance.
Warped Forest: Endermen spawn often here, so make sure that you build with blocks they cannot pick up. Make ceilings two blocks high so that they cannot teleport or spawn inside. Because ghasts, magma cubes, piglins, hoglins and most other Nether mobs do not spawn here, this is possibly the safest biome to stay in.
Basalt Deltas: Building here is a real challenge thanks to the pockets of lava, magma blocks and basalt that spawn on the floor, and the uneven pillars and spikes. You also need to watch out for magma cubes, which deal high damage, even the little ones, and some knockback.
Soul Sand Valley: You need to change out the floor from soul sand and soil to avoid being slowed down. Watch out for ghasts and skeletons: they spawn most frequently here, and the natural terrain can slow you to a crawl.
Nether Wastes: Read the info above for protecting the portal. Piglins, magma cubes and ghasts spawn here, but it is a good place to find quartz as it is not obscured by any nylium.