Most video transmitters used for fpv racong are analogue as they are much cheaper and have low latency. The max resolution for analogue systems is about 700TVL, but you can get some cameras that output 1000TVL although there is a max resolution an analogue video feed can have which is around 700TVL apparently (I’m not an expert here) so using expensive HD TV goggles for fpv is abit pointless as the max resolution is about VGA quality (700x480). I talk more about this in my fpv camera guide:
If you want us video then you need to use a digital video feed, currently the chepest you get is about £500 (Ammon conned). But there are esomewhre cheaper diy versions that involves using two raspberry pi and long range WiFi cards.