Thank you for your replies, the three of you.
@shahmoradi Part of that paragraph sounds familiar. MFE? I previously read about SOA and AOS, though unfortunately nothing definitive and with very opinionated conclusions for different scenarios.
In any case, going with your advice, and in line with what @sblionel mentioned (use of the same arrays in each loop iteration), parameters will do. I might come back at a later point and see if there are any improvements around the use of the arrays.
@FortranFan That is a very concise, useful TL;DR regarding abstract interfaces. Will follow it from now on, unless someone complains.