AirPlay from iMac to Tv or apple Tv

Assuming the TV supports Airplay 2 then yes, you can go direct from the iMac to the TV wirelessly, both the iMac and the TV must be on the same network. Please check with your TV's support or check the manual to see if it supports Airplay 2. If it does, please refer to:

Use AirPlay to stream what’s on your Mac to an HDTV - Apple Support

and also

iOS - Home Accessories - Apple (note this is a list of AirPlay 2 enabled TVs.)

If your TV does not support Airplay 2 does not then you will need an Apple TV streaming device, I'd recommend the Apple TV 4K model.

Another option is if the computer is close enough you can set the TV up as an external display and connect the iMac directly to the TV's HDMI input.

Yes, to Apple TV connected to your TV.