There’s a nice Buescher Grand trombone for sale near me with the elaborate gold and silver contrasting engraving. Is this a collector only, or is this a horn someone would really play?

Depends on what you want to do with it.

It probably has no slide lock and no bell lock. I'd hesitate to use it either on the march or in a big band with a lot of mute changes.

It will have a "smaller" sound and may not be a good blend for a concert band or symphony orchestra with larger bore instruments.

If all you want to do is play it in a small ensemble or at home it would be fine.