Synology?

[Enquiries]

I currently have a Mac Pro 5,1 that's stuck on an older version of MacOS so I'm thinking about my digital future. My current setup has 8TB of internal storage with just about 4Tb being used. It's an 8 core 2.0 GHz with 42GB of ram. I have two LaCie external 8TB drives that I use for Time Machine backups (I swap them every month and leave one offsite).

In thinking about retiring the desktop I have been researching NAS for a few months now and I think I've settled on a DS420+ with three (3) 4TB IronWolf HDDs, probably running SHR. I intend to use the 8TB drives as backups for the Synology, swapping them out monthly. I have a MacBook Pro that I will transition to as my primary computer. I store lots of photos and I have a very inefficient method of transferring them from my camera or iPhone to my Mac Pro currently. The majority of my storage is photos that I look through on occasion. In the future I hope to do more photo editing and sorting. Since the Mac Pro is older it doesn't import photos through Image Capture as HEIC but as jpg. So I load pictures from my phone to my MacBook Pro to a Dropbox folder that syncs to the Mac Pro and then copy them from there to the folder where I want them stored. I also share my Mac Pro folders so I access files, copy, and move them on the Mac Pro through the MacBook.

So, I have questions/concerns:
1. Why not just continue to use the Mac Pro as a file repository? Although inefficient, it does work...
2. My iTunes library is LARGE so I can't put it on my MacBook. Is there an elegant solution for having files local to the MacBook when I'm not online and able to access the Synology? Maybe there isn't and I just use my phone or iPad for those times.
3. Is it possible to upload single photos from the iPhone to Synology.
4. From watching your videos I don't think SSD cache is of much benefit to me. I don't access the same files over and over. Is adding/maximizing memory a better bang for my buck?
5. How many years before I should plan to upgrade a NAS?
6. Any opinion on just getting a newer Mac and duplicating the system I have now?
7. Are there any things you think I should know before I jump in. I am reluctant. This is new to me and I feel some anxiety about it.
8. Do you think there's another storage solution I should consider?

[ed]

Synology DS420+ with 3 drives in SHR(RAID5) will be a good solution with an easy option to expand.With a NAS in place, everything can be centralised. Replace dropbox, manual backups and external drives.You can install the iTunes app on a NAS and link it to your devices.You can automate all multimedia uploads to the NAS as well as select individual files to upload. Synology makes it easy.SSD cache might not be something to consider for a home environment. I would slightly speed up Plex, but in reality, it only helps with virtual machines, web server and 10+ user environments.With plus series NAS, you do not need to think about upgrading for about 5 years (replacement models come out every 2-3 years if you do consider early upgrade). Many people even last 10years in most cases.Keeping a MAC system or upgrading it would not simplify any backup process neither the accessibility and option to share thins. NAS is easier.If you want a future upgrade option to 9 drives then you can also consider DS920+.I hope this helps.