I remember years ago there was a place on Angel Island that rented Marin Bobcat Trails and two-wheeled trailers to go with them. Those bikes were fairly low end, mix of AceraX and Alivio, and Angel Island is not flat at all. I think your Neko and 8.3 will be fine regardless who does the towing.

How did the Neko and 8.3 compare to the Trek 7100 for you?

It looks like in the photo that the fork on the Neko has protrusions for disc brake caliper so it is possible to add it to the front at least in the future. I don't know whether you have the requisite mounts on the front wheel for the rotor though.