Advice for HA storage (Homelab)

Hi there

I'm in a need for some advice regarding HA storage for my homelab in case of hardware failure on the nodes.

What I have:
Synology NAS DS918+ 20TB RAID1
1 Dell Optiplex 7080 - i5-10500T 64GB ram, 1 256GB nvme disk with option for SSD disk
1 Dell Optiplex 7090 - i5-10500T 64GB ram, 1 256GB nvme disk with option for SSD disk
2.5GB network with unifi switches. USB-C is used on the above devices to connect.

What I run:
MariaDB in LXC (20GB in size)
Hoarder LXC
Nginx Proxy Manager LXC
Pihole LXC
Apache (Wordpress sites)
Guacamole LXC
Proxmox Backup Server which backup to Synology NAS over NFS.
Docker in Debian VM with various containers like Home Assistant, Jellyfin, MQTT, Z2M and so on.
Windows 11 VM with Blue Iris moving older recordings to Synology over SMB.

What I wish for:
If one container/vm or node goes offline, quickly failover VM or LXC to other node with minimum downtime.
5-10 minutes downtime is okay.

My random thoughts:
Run qdevice on Synology for quorum if cluster needed.
Ceph needs separate high speed network ? Or at least 3 real nodes ? A lot of data writing back and forth
Replicating needs ZFS, which needs more RAM ? Can it work with a single disk ?
Problems replication a MariaDB database ?
Is NFS shared storage fast enough ?
Worried about burning through NVME disks
I know the Synology would be SPOF.

Your thoughts on running HA storage in a homelab with 2 nodes ?
What would be the best setup for HA with the hardware I got and the stuff I run ?