I am not certain how important any one of them is as opposed to the others. However, lots of hawks babble incessantly about the need to keep all three at top levels.
The idea is that with the Triad the USA will have the ability to strike back even if a first strike hits the USA. Any potential rival must take that into account as they do the cost benefit analysis of using a nuclear weapon against the USA. None of this is classified or abstruse. It’s all been common knowledge for people who are even just a little bit interested in national defense. I understand why a newbie to politics, like Trump, is stumped by this subject. Wife shucking and bribing Democrats has been his forte. Now, the rich dilettante can try to find out about the Triad, a strategy that has been one of the USA’s most important defense tools since the Cold War.