Is it weedy? Depends. If you like it and it spreads, does it then become weedy? Most Goldenrods do grow from underground stolons, but not 100 plants or anything. More like 6 or 7. There are several kinds. There is a flat topped kind that blooms early and the more cylindrical flowering kinds that bloom later. All of them seem to attract lots of pollinators.

So far as not a lot of space, keep in mind these are 2-3 ft. tall and shade an area about as wide. The good news is that they can be underplanted with annuals that can take shade, or even spring bulbs that tend to have foliage that disappears when the G-rods are growing tall.