I made a mod where you need an Ad Astra Netherite suit to explore the Nether. Since it's not vanilla-friendly, I'd recommend a mod that adds an Overworld Netherite recipe or an Overworld Netherite ore.
the following mobs are safe in the nether
1.blaze
2.magma cube
3.zombified piglin
4.zoglin
5.enderman
6.ghast
7.piglin
8.piglin brute
9.skeleton
10.strider
11.wither skeleton
12.hoglin