I soften for but do not filter mine.. I dont have 'hard' water per say, but do have iron and iron bacteria (leaves the rust stains if not ran through the softener)
But, if the test comes back good, I would think the most you would need to do is a standard string-wound 'sediment' filter. No need to UV bugs that arent there

Instead of using one large filter, I would split the line into 2 parallel ones and one use 2. You can run 2 of the standard 12gpm slightly smaller ones together, or better, 2 24gpm ones that are more than your flow rate and alternate. That way you can bypass one while changing filters and not have to shut off the water.
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Heres a 4 filter system with 3 in parallel..
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