Which SBC (RPi 4, RockPro64, Odroid N2 or other?) for my first NCP install? (good performance, security and support)

Hey there!

I am planning my first SBC project and decided I want to build my own cloud using the awesome nextcloud software and specifically nextcloudpi. After already doing a lot of research I kind of have an idea for how my system should look like:
I want to put 2 HDD’s into an external enclosure with RAID 1 support for redudancy like the MEDIASONIC proraid hur5-su3 or the TerraMaster D2-310, hook them up to the SBC of choice via USB 3.0 and use a third external HDD for weekly backups that are held offsite. Maybe I want to upgrade the size later to a 4+ bay with RAID 5 but not for now.
Regarding SBCs I narrowed down my selection to the Raspberry Pi 4 with 4 GB, the RockPro64 and the Odroid N2 with 4 GB because I read good things about them and they seem to have good hardware.
However I read different things regarding their performance and support and I wanted to check back with the community about your experiences. Also security is a topic for me as data will be exposed to the internet. Regarding support I know that there are official builds for RPi 4 and RockPro64 and from what I read so far I think it would be best to run NPC in docker on the Odroid N2. Is that right? How much does that decrease performance?

Do any of use any of those boards?
How was the installation procedure?
How is their performance?
What did you do to make them secure?
Is there anything else I should pay attention to?
Does my setup with a RAID 1 make sense?
What is the expected speed and where is the bottleneck?
And lastly, did I miss any amazing board that is comparable or better?

I know that is a lot of questions but I would be very glad if you would even answer just one of them!

Thank you so much!