My question entails the new update 'vanilla' nomenclature of numbering height below y=0 (being ground level) could possibly conflict with CubicChunks...if I were to create a pre-1.16 world (upon any Minecraft version which CubicChunks directly applies; that being both Worldpainter CC plugin itself and Minecraft CC mod) with height of 384 and use an effective utility app that converts worlds of older versions (e.g. 1.12.2) to the more recent version (e.g. 1.17+).

Although it seems that I should be capable of figuring it out myself through trial and error. However, my laptop is very ancient--predates the abacus-- especially compared to the most modern computers that are now available. Therefore, I must ensure myself to have a solid, well-assured preliminary plan and setup... before I create/merge to a minecraft world on Worldpainter...since that it takes decades for it to finish.

Having to wait 17+ hours to only discover that all the work and wait-time thereafter became to be a error or even a crash. It became behoove of me to overcome wasted time and effort by having all--if not most--issues resolved. Tech4troops, a Veterans program, gave me this s-l-o-w laptop... guess they don't account for impatient vets like me--mental included--who use Minecraft as the rapist...sorry, meant to type 'therapist'.