If it’s mainly road with the odd bit of farm track, you’d manage fine on a road bike with rigid forks/vee brakes.
I’d concentrate on getting a good s/h bike rather than zero in on a road/offroad bike especially if your planning mainly road riding. As with singles, more recent kit, good wheels and a frame that fits are more important than diverting the budget into a heavy suspension fork or disks.
I ride mainly road with the odd bit of track on a bespoke 700c wheeled road tandem with 3 vee and 1 drag brake. We’re not underbraked (even fully loaded when touring) and rigid forks are fine for gentler track pootles.
You can get some very nice s/h George Longstaff or similar bespoke machines for around £1000 – £1500. Often very low miles but make sure you get something as recent as possible to avoid buying into obsolete systems.