hi @RedBoyforCE welcome to the community 
I’m sorry no idea about snap but with my nearly 5y long experience with Nextcloud and 20y in IT jobs I think I can share some insights.
I used Docker for my NC installation from the beginning. AFAIK it’s similar to snap and has it own issues but it is far more customizable and there are multiple solutions
- starting with new and shiny “All-in-One”
- over traditional "community Docker image (I published a nice guide few days ago Nextcloud docker-compose setup with notify_push (2024)
- and many others.
In my eyes Docker (or maybe podman) is very good solution for self-hosting because you can easily run multiple instances side-by-side using different settings and versions - e.g. I’m running two Nextcloud setups, one for production with real data and one where I test upgrades and new apps (and third one just for throw-away testing) on an old desktop PC similar to your.
Docker allows to store data wherever you want, so you could store apps and database on fast SSD while all your files, photos and backups live on cheap magnetic disk (see Docker persistent data).
There are more solutions like Hansson VM and the “traditional” bare-metal install as most powerful but most complex install (in my eyes) - no additional complexity because of virtualization but more problem due to upgrades, package dependencies backup and restore.
I think you will find good Nextcloud installation tutorial for almost every common setup today. I would suggest you choose the one you are most comfortable with - there is always a way to move your installation to another server running different hardware or software. It might be harder or easier depending on your knowledge or software but as long you backup all important parts you are on the safe side.
Regarding your storage design - one can discuss days and weeks about it but this doesn’t address maybe the most important topic in your plans - backup. I doesn’t really matter which level of RAID and how many disks you add to the system your still suffer form “single point of error” which is still your server… in case of disaster like fire or flood, human error killing all the data (e.g. you as an admin run “rm -rf” command in wrong place) you will loose everything… for this reason you definitely should plan for backup on a second system - which is OK to run in the same place and another “offsite” backup outside of your home - this could be a simple USB drive you give to your parents, store in the holiday home etc…
I tried lot of different configurations and for the moment my preferred setup looks like “very simple Nextcloud ‘server’” running with one SSD and one HDD. This one preforms daily backups to a NAS running in another room (with RAID)… from there I do pseudo-automatic backup to 3 different USB disks which remain offline most of the time and only connect with the NAS for backup every 3 disk (each week another disk). This is definitely nothing professional but I’m pretty confident this backup strategy will survive most even catastrophic scenarios I can imagine… Definitely recovery is not really easy but I know I can recover the majority of my data if one of the systems survive the incident - I loose few hours to maximum 3 weeks of data maximum (if only the oldest USB disk survive)