Beets for cleaning up the tags and self-hosted navidrome appears to support multiple artist tags. The web interface of navidrome definitely supports filtering by both albumartist and artist (the latter will include albums and tracks with multiple artists). I assume this is what you are trying to achieve by using a visual artist tag? If you just want to rename an artist but keep the underlying artist tag, that can probably also be achieved with beets.

This link shows the details of how navidrome handles tagging: https://www.navidrome.org/docs/usage/library/tagging/ The issue if you don’t want to use the navidrome web interface is that not all clients support browsing by artist I suspect (and often use albumartist, which I personally prefer). I use supersonic which I doesn’t appear to support it, but there’s also Feishin and a bunch of mobile clients you could use (or open a feature request on supersonic github).

Replaygain will be supported by most clients (not sure about the navidrome web interface).