Synology NAS Recommendations

Hi, I have a quick question. I was hoping someone could help me with this. So, I have approximately 30 TB of storage on hard drives and SSDs. I want to transfer all that data onto a Synology NAS and back up my MacBooks, Google Drive accounts, and iCloud pictures. Per year, I will be adding around 200GB or so onto the NAS. I also wanted to future-proof my system and was wanting to implement Raid-5 or Raid-6. Given this info, would you recommend that I buy the Synology DS1821+ or DS1621+? Or is there a different Sinology you would Recommend I buy? I want to fill only some slots. I was thinking about putting in around 4 16TB drives in to start. This is also just an at-home unit for me. I hope I can get some guidance and or recommendations based on the following info. Thanks

I would go for the DS1821+. The $100 premium, is completely worth it for 2x more bays in my option!

You can start with 5x 16TB Drives, then just add space as required

Thanks for the recommendation. Does it make more sense to put in 12 TB drives instead since, to my knowledge, the maximum storage for the DS1821+ is 108 TB?

So you would want to setup RAID5 for under 6 drives, then RAID6 for up to 12. So with that you will hit the max 108TB