my concern is that I install a distro this year and want to switch to SteamOS later, but would have to start over with customizations, etc. in the new distro.

I wouldn’t sweat that at all.

I switched distros last week, didn’t like the new one as much as I thought I would, and switched again a few days later. It’s not that big of a deal. Install some apps, reload your files from a USB stick. It’s not a major commitment.