If you need really good Office Open XML support outside Microsoft Office, then you should go with OnlyOffice. Be aware that it does not support encrypted storages for now.
I installed both containers (CODE/OnlyOffice) on a Docker Host and connected them to my cloud. You can run both plugins in Nextcloud so you can try both without a problem. This is especially useful if one document does not display properly in one of them.
Memory consumption also depends on how many users/documents you want to open up at the same time. If your load is rather small, a Docker host with around 4GB RAM for both of them will suffice. If you have more users/documents open at the same time, you will definitely need more.