I am investigating optimal solution for dual controller NAS. I want to achieve XCP-ng pool HA and with 3 nodes, redundant switching, MLAG and storage multipathing (iSCSI or NFS) the weakest link in the chain seems to be single controller storage. Things crunch down to QNAP, Synology and TrueNAS (at least in here in Europe where I live). I’d prefer ZFS so Synology went down to 2nd place. I’ve watched Tom’s video with Synology SA3200D dual controller (Active-passive) failover testing (https://www.youtube.com/watch?v=dwIO6gZnTXc&t=1155s), and switching IPs beetween controllers looks bit awkwardly. TrueNAS failover solution (https://www.youtube.com/watch?v=obZOgp_jSFc) with CARP VIP and Active-standby looks much more better to me (I might be biased because I have experience with pfSense HA which works perfectly to me not loosing a single ping in failover). I could not find any video on QNAP failover testing, and beeing Active-active configuration I assume it is something different. Does anyone have any expereince or advice, please?
I avoid QNAP because of their security issues and I don’t know anything about their HA. TrueNAS is a very solid option if your budget allows for it, Synology is a good solution as well.
Thank you for heads up! Synology is an option for sure. Although I wish on TrueNAS closest partner is 1600 km away. So I am looking into other solutions available locally (like Dell ME5 series with iSCSI controllers). Hope to post my setup and experiences soon. 
As I mentioned in the “How Does TrueNAS High Availability Work?” video you linked above, it only works with their hardware.