>>7459349HCM Pro (pic) was a Bandai toy division line from the mid to late 2000s, they are 1/200 so most MS end up around 9~10 cm, which is about the height of your TF legends toys. They are prebuilt but they use snapfit construction (no screws) so they might be quite fragile. They are cast in 1 color plastic and fully painted too, so susceptible to paint scratches.
There's also the Bandai candy toy lines, namely
Gundam Assault Kingdom, Universal Unit and currently G-frame. These are cheap and good like candy toys are. Here's an ad for G-frame.
https://youtu.be/oQo7M7z2PHsG-Frame is probably the most accessible since it's the current ongoing line.