It's just another modern ICBM, probably with a fast boost, suborbital countermeasures and terminal evasive maneuvers.
With a 1000 warheads per side, this doesn't really change the MAD equation. A recent Chinese study that showed you need a really serious shelter depth to survive modern nuclear attack is actually important. It showed that Russian fancy "elite city shelters" aren't nearly deep enough.
"China research finds flaws in US nuclear blast equation to protect shelters | South China Morning Post"
https://amp.scmp.com/news/china/sci...finds-flaws-us-nuclear-blast-equation-protect