oker wrote

For all I know, the EAP120 support roaming. But user disconnect with the AP first then connect the next AP in a short time. It isn't seemless.

That AP is already EOL for a long time. It doesn't support 802.11k/v/r, it doesn't support MESH. It does support feature, when AP can disconnect the user based on signal strength, which is pretty important, so basically, it is some kind of roaming, but in fact no, it doesn't support Full roaming via 802.11 or MESH.