Well, you're in the right community.

like the power and gas are made right next to your farm and you can just plug into it with a 100m cable

They are. The gas fields need power anyway, so they run the lines carrying gas to your city right alongside the lines carrying electricity to your city. Since the solar, the wind turbines, and the gas fields all need serviced from time to time, there are road along them as well. Dropping a small settlement here and there along the way reduces the housing burden, the traffic burden, and all the other burdens of rampant urbanization.

Now you just need to get water for your crops from elsewhere. I figure you’re not gonna want to use well water, because if there were enough water under your farm to feed the crops, you wouldn’t need irrigation.

Water wells might be the largest source of irrigation water. If they aren't, they are second only to surface water: lakes and rivers. Nobody uses treated water for irrigation.

But if we’re talking about 300 people’s houses, we can do better than a 300 off-grid solar setups. We can build an economy of scale.

Yeah. We tap into the lines running from the various power sources in the countryside to the industrial centers, and use them to power our pleasant, rural settlements.

We can build row houses

Yeah, that's that medium density stuff you were talking about. Not dense enough to justify infrastructure investment into public transit, but too dense to simply be happy in your own home. The kind of housing that maximizes tax revenue to governments and rent to slumlords, while minimizing public services. The kind of housing that carries the worst attributes of both the suburbs and the urban centers, with none of the benefits of either. Contrast with rural living: massive improvements in wireless internet and a building Work-From-Home culture means you don't have to commute anymore. You don't have to go into the central office for your daily grind. Less commuting, less travel, enough space for a workshop, a deep freezer, a craft room. An actual vegetable garden: A garden where you have to decide what to can, freeze, or dehydrate for winter. A garden that feeds you for months. Not the potted plants on your back porch that might give you a couple tomato slices for a burger and some peppers to add to a salad.

We can run trams instead of electric cars and waste far less energy moving metal vehicles around.

Medium-density row housing doesn't provide enough demand for trams, let alone trains. You might get buses. You don't get the benefits of public transport until residences go vertical and you're literally living on top of eachother.

Better than public transport is "Just stay home". But that's not really an option when you don't have space to do anything at home, and you have to travel for any hint of enjoyment.