For the best value overall I'd recommend Onedrive 1TB Family (up to 6 users, each 1tb). Though if you don't need lots of storage I'd recommend Google One 100gb, or at a stretch 200gb as I find the user experience better and the photo creations/editing quite good compared to Onedrive though if you can, pay annually so you only pay the equivalent of 10 months instead of 12. But if you want to download your photos from Google One at any point, don't use Google takeout. It's trash. Put every photo into an album (think there's a set size for single zip file download) and download each album directly from the website.
So my recommendation is extremely specific, it's limited to you having physical access to an argos store then transport, timing. stock and petience come into play. A few times a year Argos (in the UK at least) sells Microsoft 365 1TB Family (6 users, each 1TB) bundled with McAfee Total Protection (up to 10 devices) both for £39.99 a year or £3.33 a month. You can buy 5 maximum as that's the most you can stack to your account.
Presuming you live in the UK and have a nearby Argos store you 're able /willing to visit, start saving in increments of £40 up to £200 max. Then keep your eye on price alerts for the item. I used hotukdeals but the Argos website itself might work too for that. Weirdly they don't deliver it, you have to actually go collect it (pandemic or not). This could be a sales tactic to force you there to impulse buy, but, if you resist and share the cost with just 1 other person it's roughly the same price as the cheapest Google One monthly price but you get all the premium office apps, random deals (way better than Google One as I pay for both). During l lockdown I was given 3 months of photoshop and lightroom access for free, 3 months of creativelive access which I used for photography classes and something else. Because I already subscribe to photoshop and lightroom I added the 3 months onto my account and saved £29.97 instantly. Now with Samsung and Microsoft partnering it may become more seamless too. Also each user can have the office apps on their laptop and phone. McAfee Total is just a side bonus imo, you can also use it on your phone and laptop and it has dozens of free features which are well worth it such as a VPN, backup, battery boost, storage cleaner, find your phone etc, etc. But since it sells for £25 you could just sell it on ebay for £15 - £20. I just shared mine last month with my sis and we're good to 2026 now haha.
Oh yeah and as pointed out Amazon Prime Users can get free unlimited photo storage with amazon photos but have to pay £1.59 a month more if you want over 5gb of video storage. Also they won't offer free unlimited, full resolution forever so I'd be wary on relying solely on that. I can just picture some poor soul with 100tb of photos uploaded and are then given the bad news that 100tb will cost £99.99 a month unless they download it all.