Oof, I like where your heads at, and wish I had the budget to worry about it.
Source matters more than regularly available filtration methods. I've had cave water that was still cold after a whole day in the summer sun. A man I met never drank anything but his own personal well water. It did the same, stayed cold all day in my metal cup strapped to my bicycle-before those double walled cups were a thing. In Nevada. In August.
Anyway.
Prefiltering before you store aboard is ideal, I'd do as much as possible before your intake.
RO is top tier, but super wasteful. Maybe you can find places to pull it off. Maybe setup an RO system for use when you can, and an alternative when you don't have a good drain or can't afford to dump 3/4 of the water you're pumping. I'm also unsure of the energy use of RO.
Water hardness is also a consideration, some areas have such hard water it'll just jam your **** up with garbage real fast. I think you have to custom tailor your softeners to your source though.
UVC is great for biological nasties, so you want to hit it with that before you pack it around for sure. Perhaps there's an in-tank option? Or at least an in-line?
Your tank and lines are likely plastic, so use that charcoal filter as close to your tap as possible, to nab the microplastics and funky offgassing.
I'm kinda just sptiball rambling here. We fill a 5 gal cistern with whatever we can fit it under. Haven't died yet, but I can't say it's looking great. Maybe someday the pub will let me fill it up with beer