You use a
valve like this on the drip to change the amount. You may need a slightly different size just like with the bulkhead. It will need to be after the filter so that the filter always has full pressure, and any clog in the filter (unless it's completely) doesn't slow the water supply. This must be ABOVE the water line. If it is not and your house loses water pressure, you'll contaminate your drinking water as tank water slowly gets siphoned back in.
The drain is below the water line (obviously). I then put a 90 degree elbow pointed up and its tip is at the water line. I suppose you don't need the elbow, but with both I'd think about getting a
strainer like this if you have any fish that could fit into the pipe. Just make sure if doesn't start to clog. You could put in two drains just in case if you want to be extra cautious. In that case, have one slightly above the water line as an emergency. That way it won't develop algae or anything else blocking it at the same rate as the other, and then when the water rises a bit to drain through the second, you'll know the first is clogged.
The water automatically balances itself with gravity. Water comes in then as the tank level rises, the water reaches the drain and exits with gravity to your sewers. This is how sumps work too. There's one pump sending water up and it automatically comes down with gravity, since keeping two pumps in exact sync would be impossible in the long term.
The only other big concern is if you have a septic system instead of city sewage. It's possible you'd overflow it as I know that's possible, but I'm not an expert on them and have never even lived with one. Another concern is water contamination during flooding so if you have a hurricane, you probably want to shut it off in case the city sewage floods into water supply. I'm fortunate enough to not have to worry about that one either.