Depends on your networking setup. A good switch will simply refuse to route packets between clients on different VLANs, and hide the existence of the tags that determine which VLAN a host is on.
A bad switch or router (which almost certainly includes a ton of crappy home APs and routers, compromised by the same actors who ship these devices) could let clients see VLAN tags and ignore them.
And an Ethernet “hub” does no filtering at all.