They are basically constants where you can define reoccurring sections once and reference them multiple times throughout the file. A processor will then resolve these. As gar as I know, there is no comparable concept in JSON so they could get lost in translation

I could see some problems when working with yaml anchors, otherwise the conversion should work fine. But yeah, using a good editor should fix most problems and would be much easier

If we play in person, we mostly go with simple dry-erase marker on a battlemap. It is easy and flexible, although not very visually impressive