I'm not sure what you mean by "PCB channel"; if you're using microstrip or slotline either would suffice. Generally, waveports are used for external excitations (that come from outside the domain), while lumped ports are used for internal excitations -- although these are somewhat flexible, as well.
Mostly, it is a matter of preference and accuracy to modelling your exact situation.
Wave Port
Represents the external surface through which a signal enters or exits the geometry. It is effectively a semi-infinite waveguide attached to the model. This waveguide has the same cross-section and material properties as the port. Wave ports are placed on this interface to provide a means to link the model device to the external world.
Lumped Port
Represents an internal surface through which a signal enters or exits the device. It is effectively a lumped element for exciting the device and measuring S-parameters. For designs with only lumped ports or a combination of lumped and circuit ports, the Advanced Solution Setup, Options tab includes an option to use Enhanced low frequency accuracy.
I'm not sure what you mean by "PCB channel"; if you're using microstrip or slotline either would suffice. Generally, waveports are used for external excitations (that come from outside the domain), while lumped ports are used for internal excitations -- although these are somewhat flexible, as well.
Mostly, it is a matter of preference and accuracy to modelling your exact situation.