Is there any specific way to force my CSS326 to live on a specific management VLAN and acquire its address via DHCP that way? It may be hackable by setting the default VLAN ID of the switch interconnect ports to the specific VLAN but that feels like a hack.

I would keep the vland default ID at 1 on all devices and use specific other vlans for all traffic including a basehome vlan or a management LAN.
I have found that I have to assign the lanip on devices manually. Not sure how to ensure auto assignment of the current LAN in any other way???

I think it would just be helpful to know (be documented somewhere) or configure which VLAN the switch lives on. It is probably VLAN 1. This may be because I set "Allow from VLAN: 1" though.