The CPU and more RAM (better on the DS220+)and expansion with SSDs for Read/Write cache (only available on the DS220+). Also different is the long term support plus you can remove the disks using hotplug trays. Disks are locked with screws in the DS220j. I advise not to invest in anything with j in the name, these NAS are not good options for NAS, they are very limited in regards to anything. I strongly to advise in investing in a 4 bay NAS, expandability is much better plus you have the possibility to also run the NAS with better hardware redundancy and you can also use smaller drives that cost less to expand. With a 2 bay NAS you are forced to buy two simiar sized disks and if you want to expand at a later time, you are forced to replace two drives. When you start with two drives on a a 4Bay NAS, you can then expand by adding additional drives and you can then convert a RAID1 mirroring config to a Synology Hybrid RAID redundancy config. A great and cost efficient NAS option with 4 bay would be the DS418, it has a quad core CPU and 2GB of RAM (cannot be expanded, but it is less expensive than the even more powerful DS420+)

Apps that runs on the NAS? See section Packages https://www.synology.com/en-global/support/download/DS220j?version=7.1#packages

I would advise against buying a Synology NAS solution with j in the name, the products are not well equipped. If possible I would also choose only a 4 drive NAS, they are a bit more expensive but you can work with more than 2 hard drives, e.g. buy three smaller ones and a fourth if you need more space. With 3 hard drives you also have extended hardware failure protection with RAID5 and you don't give away half the storage space as with a two drive NAS with RAID1. My recommendation if it absolutely has to have two drives would be this NAS (4 core processor, 1 GB RAM): Synology DS218play But as I said, I would take one with 4 drives, which are also better equipped (more RAM, better processors), e.g. one with a 4 core CPU but even with 2GB RAM: Synology DS418

CMR. There should be enough material on the internet to read about SMR vs CMR.

Technically it doesn't matter, lying down is of course also possible, but I would get some relatively large rubber feet from the DIY store, transparent ones, so that you don't hear the vibrations of the plates so clearly. I strongly advise against the j devices, they are simply rubbish, my recommendation is clearly also for 4 bay, but if it can only be 2 drives, then by all means take something like this, you simply have much more of them and they don't cost much more. For 2 bay, I would take this one, it has 2GB RAM and a 4 core processor and the disks are easy to install and replace in drawers without tools. Synology DS218 (0 TB) If a 4 bay is possible, I would go for the DS418, it is more expensive, but you would also have the option of installing smaller disks to achieve the same storage size, because you have 4 disks at your disposal: Synology DS418

A big advantage of a NAS is probably the data security. This is particularly effective due to the redundancy in a 2-bay NAS. (The data is stored on two separate hard disks in such a way that it can still be read if one of them fails). I can therefore recommend the DS220. Synology devices are, in my experience, very tolerant when it comes to HDDs - different makes and/or different capacities can be combined. Nevertheless, I would recommend two identical disks.

Yes. VG

The memory cannot be expanded.

Definitely not. The performance of the NAS is simply too low for that. VG

I don't know exactly which manual you mean. https://global.download.synology.com/download/Document/Hardware/HIG/DiskStation/20-year/DS220j/ger/Syno_HIG_DS220j_ger.pdf for 3.5" hard drives --> No for 2.5" hard drives --> Yes

Scheint ohne Probleme zu funktionieren, schau mal hier: https://www.reddit.com/r/synology/comments/n7xz7h/plex_vs_emby_media_server_on_a_synology_nas_in/

Unfortunately, we do not have any information on this at the moment. As soon as the supplier has news on this, we will adjust the delivery date in the online shop.