I have the impression that HPL and REH tended to converge on a non-anthropocentric conception of the cosmos, although only HPL truly developed this paradigm. It is true, however, that even though he was agnostic, REH never renounced Christianity entirely.
Thank you very much for your answers. ^^

The question could also be extended to CAS or CL Moore, of course...

To what extent did HPL and REH converge on atheism/agnosticism and sexual morality (including marriage) in the context of the "puritan conscience" of the time (in the USA)? A very broad question, certainly... ^^'

Indeed, I remember in particular Howard mentioning to Lovecraft simply a "love affair" about Novalyne Price... Thank you for your quick answer! ^^

In a recently discovered 1933 letter to E. Hoffmann Price, Robert E. Howard asks if H. P. Lovecraft is married. Does HPL mention Sonia Greene and their marriage, in his correspondence with REH or with Clark Ashton Smith or with others correspondents like C. L. Moore (I don't remember or no longer) ?