To anyone else wondering: Yes you can install regular ACF (using zip file from ACF website, not wordpress.org due to recent hack/loss of control of their data). When regular ACF is activated, the acf pro installation automatically is deactivated, and it does indeed retain all ACF fields/post types etc you had previously set up [presuming field types exist in regular ACF; Meaning, as for my setup- none of the additional features of Pro were used, so this worked fine for the test/dev site [and this can be marked resolved]
