For several years now, the focus has been on optimizing software. Apple has been a trendsetter in that regard. The OS in 2020 is likely to be about the same size as the one today, and it runs beautifully on much less than 4 GB. Barring that, 4 GB should be plenty. Enjoy.
Having updated two Mac Minis from 4GB to 16GB there is a huge increase in performance. Just like when updating from mechanical hardisk to SSD.
OP: Get as much RAM as possible and a SSD.