[Fat Abe]

I have never bothered with definitions of hard or soft SF, although these concepts appeal to certain readers. The Cambridge Companion to Science Fiction (ed. by Edward James and Farah Mendlesohn) deals with the subject in chapter 3, section 13, of the book. What follows are excerpts from the book:

In 1999, long-time Analog editor Stanley Schmidt, heir to John W. Campbell’s job, remarked:

Lately I’ve been saying I’d like the term ‘Hard SF’ to go away. Too many people use it to mean something much narrower than what I mean by it . . . science fiction is simply fiction in which some element of speculation plays such an essential and integral role that it can’t be removed without making the story collapse, and in which the author has made a reasonable effort to make the speculative element as plausible as possible. Anything that doesn’t meet those requirements is not science fiction at all, as far as I’m concerned, so there’s no need for a separate term like ‘Hard SF’ to distinguish it from ‘other’ kinds of sf.
...

So if the sub-genre is a contentious conversation in constant flux, how do we avoid solipsistic definitions that amount to knowing it when one sees it? We return to a modified conventional wisdom for our definition: a work of sf is hard sf if a relationship to and knowledge of science and technology is central to the work.

... Before science can be incorporated into hard sf, it must be stripped of its mathematical bones, so that – no matter how accurate the text – science is used as a mythology. What science gives to hard sf is a body of metaphor that provides the illusion of both realism and rationalism.

By reputation, hard sf is science fiction that gets its science right and has a certain hard-nosed attitude. Its plots and backgrounds are in the tradition of Hal Clement’s Mission of Gravity (1953), its attitudes in the tradition of Robert A. Heinlein.

Kathryn Cramer was the contributor of this section of the book. Bless her for condensing a lot of information into a few pages. She is so right about the writing being "stripped of its mathematical bones." Ronald Reagan was one of the least intelligent presidents in the history of the US. One wonders if he could even derive Pythagoras' theorem. Yet, out of his fascination with science fiction, and the influence of certain SF writers, we spent billions on the Strategic Defense Initiative program.

My recommendation to the OP is to ignore sub-genre classifications. Just read the great classics of SF, such as Theodore Sturgeon's More than Human, or the very advanced thought experiment, Camp Concentration, by Thomas Disch. Any list of the 100 best novels in SF will give the reader a better start in the field than niche examples. The latter is analogous to confining ones exposure to Indian food to just eating lamb dishes.