Will manylinux1 wheels compiled with older numpy (say 1.14) work with manylinux2010 wheels?
What is your recommendation for downstream projects that depend on Cython/numpy to do?
Do you have a document we can read?
I don't think there will be any problems apart from pip versions, the reason for using manylinux2010 in the pre-release wheels is to discover if I'm wrong about that :)
For documentation of the manylinux project, see PyPA, PEP 571, and PEP 599.