If you had the resources to run and maintain a nuclear submarine force, but were also resource limited to a single form of strategic deterrence, then yeah, you would probably go with SLBMs. This is what the UK and France settled into.

But it costs a lot to feel confident in SLBMs, especially if the top of your target list includes the USA.

Otherwise, if you're talking about the USA specifically... ICBMs should probably be considered an expensive hedge.

Finally, "optimal" depends on your definition. China has chosen a public "no first strike", while also avoiding launch on warning likely for a variety reasons. China's publicly stated "minimal deterrence strategy" (which they seem to be walking away from) was probably at least partly a pragmatic choice, driven by resource constraints. Also, for what its worth, it does seem like China is also walking away from a strict "no launch on warning" policy as well.

The lack of launch on warning (this is my speculation) was probably a combination of lack of technical capability (both ISR and C2), wanting to maintain tight central control, and wanting to play up the advantages of being "the third player".

Here's a whole recent report on China's nuclear force: https://www.tandfonline.com/doi/full/10.1080/00963402.2025.2...