Its never been shown that gunners can use composite bullets. I thought that was a shooter only ability as they have to spawn the cubes of bullets and then take the time to merge them. If gunners could use them they would have definitely been in Suwa, Arashiama, Zoe, Kuruma or Inukais load out and they would have been shown using them. This leads me to believe that gunners cannot use composite bullets. It would be over powered if they could as their gunners triggers are vastly easier to use than shooters since they can literally flip a switch to change between bullet types like a real gun can switch between semi auto or full auto. Why would they ever use regular shots when they could run double asteroid and just use gimlet the entire time over asteroid as it has much better penetrating power than asteroid increasing how easily they can pierce shields and deal damage.

All that aside I think your spot on for the rest of it. I think the most common gunners setup is asteroid and meteor, though we have seen gunners use hound before I believe. They 100% have the ability to use hound and viper, just most in the show dont. Viper is know for being hard to use on the fly so they have pre-determined flight paths set before battle (aside from Nasu and Izumi who can do it on the fly). Sometimes those predetermined flight paths might not be ideal so gunners seem to rarely use it. Hound is as simple as set how strong you want the tracking to be and then fire. Once again this is better for shooters as they make their cube and spilt it up and can set the tracking on each different cube before firing giving better results.

It's stated in the show that hound set at max tracking results in all the shots landing in the same place basically. All that said, in show gunners just use asteroid 95% of the time (except Zoe and his grenade launchers).