Did not realize there was a combo option. With that it sounds like my questions are answered!

The combo is generally just a water softener with some filters added. Look at details before buying as there is some expensive ones that are no better than the cheaper ones. Had one of the expensive ones and replaced it with a cheap one and the cheaper softener works better.

https://www.pelicanwater.com/water-softeners/water-filter-and-salt-free-softeners-with-pro-uv/

Just a suggestion but doing a search by simply typing in a question about something that you need information either just in your search area or on YouTube could have answered most of the questions you have asked. Something simple as your question No. 1 would work. No need then to wait around for someone to see your post.

If you want to remove hardness, you need a water softener. There is no "salt free softener" that's not a real thing.

If you want to remove chlorine, taste and odor and some VOC's that's a carbon filter.

If you want to remove chloramine, taste, odor and some VOC's that's a different carbon filter.

If you need to remove nitrates, lead, etc. in drinking water, that's an RO filter.

- This isn't a complete list... but what is it that you want to do?

BTW: Don't combine filters in a single unit. They each have different backwashing and maintenance requirements.

As for the plumbing:

For soft water - soften everything except the outside hoses and a drinking water run to the kitchen.

For filtered water - use an unsoftened run, to a carbon filter, that then supplies a drinking water faucet in the kitchen and the icemaker in the fridge.

On my house I have an untreated manifold (for outside), a hot and cold softened manifold and a filtered un-softened manifold (for drinking water)