temperature control inside gas oven?

I'm not sure if this is true for all gas ovens but all the ovens I have used (or installed) there is a thermostat in the oven. It has a sensitivity range. Let's say it is 5 degrees. If I set the temperature to

You'll know this is how your oven works if you just turn it on and listen. Once the oven is at temperature you will hear the burners turn off (or reduce notably). If you open the oven door for a few minutes (maybe only seconds) you will hear the burners kick in again.

Regulating the flow of gas would not work. Impurities in natural gas mean it does not always burn smoothly. Some gas is cleaner than other. The purity of your gas supply could alter from day to day. It will definitely alter from location to location.

Things to note when buying an oven, how well does it hold the heat (better means less burner on/off) and how sensitive is the thermostat.

That's about right. Older gas ovens use mechanical thermostats. Back in the 1950s, even stoves with automatic pilot lights for the cooktop burners required manually lighting the oven with a match. Then a mechanical thermostat would moderate the amount of gas from low to high, never fully extinguishing the flame.

Most, if not all, gas stoves sold today use electronic ignition. This conserves energy because there is not a pilot light flame burning

However, it's in the oven where there have been some important changes in design -- notably for reasons of safety.

Ovens with electronic ignitors may use a very hot quartz lamp or other device to start the oven burner. When you turn on the oven, this lamp comes on and there is a small flow of gas to a pilot burner near the lamp. Not until this gas ignites will the control system allow a the flow of gas to the main oven burner. The control system then cycles the oven pretty much as described by Darell in his response above. The key safety feature here is that gas will not flow to the oven burner until the ignitor comes on and the pilot flame is proven.

Mechanical oven thermostats are notoriously inaccurate. Electronic thermostats, some with multiple temperature sensors, are able to control the oven temperature more accurately and within a much narrower tolerance. Electronic control systems also can provide timer features allowing some ovens to be programmed not only with start and stop times but also to keep food warm once cooking is completed.

The disadvantage of these electronics, of course, is that one's gas oven will not work in the event of an electric power outage. One can light the cooktop burners with a match, but without electricity the control system will keep the oven safely turned off -- and the family using the backyard barbecue grille until electric service is restored.

Cheers, The Old Bear