Synology Question

I am trying to understand what the real world difference is between the Synology J series and the Plus series. I have some data and photos spread across several cloud services that I would like to consolidate. I have read the J series ram is not up-gradable. Is the amount of ram an issue? My needs are pretty simple in that I want to get things together. I do not plan to run any docker containers on this machine.

I am looking for other people’s thought process on how they decided to choose one over the other. Synology has too many models that are not obviously different.