Thanks your answer.
WOW that is a lot of backup, I am planning to purchase the QNAP TVS-h1688X with 10x8TB or maybe 10TB drives and then Seagate IronWolf 125 SSD 4TB NAS Internal Solid State Drive, 2 x 4TB for cache and 2 x 4TH for special storage (probably surveillance) outside the Raid as I will delete these files when they get over 30 days old.
Will also be installing a couple of SAMSUNG 980 PRO 2TB PCIe NVMe Gen4 Internal Gaming SSD M.2 (MZ-V8P2T0B/AM), unless you think that's a bad idea, can't have enough (too much) storage, can you?
The backup unit I have planned on the QNAP TS-832PX-4G 8 Bay which I will put same size drives in as on the 1688 and the go from there. That have to be enough for starts :-)
Not sure about this: QNAP Dual-Band Wireless PCIe Expansion Card (QWA-AC2600), will that interfere with the boats other wireless configurations. Would be nice to have a wireless connection for the NAS only to use for external units, smart phones, tables and TV's to hear music and watch movies/tv-series?
For camera surveillance I will probably go for the Hikvision DS-2CD2183G0-I 8.0MP 4K (2 pcs as I don't know how the with cover will be, will need to have both port and starboard side covered), as I can also connect those to the chart plotters and use them to safely get the 60 foot catamaran alongside in a marina, not easy to get a large catamaran along side even with a bow thruster, so these cameras will be handy :-)
Again thanks for your many answers, I know that you are probably very busy :-)