A throw that encircles the neck would likely be koshi guruma, but for me, I've found it is more unsafe when performed in uchikomi, rather than nagekomi (throwing). I had whiplash from someone doing the uchikomi part of koshi Guruma, as they had no idea what they were going & whacked me hard around the neck & head, my neck made popping noises & I had nausea/headache. It is unsafe if tori doesn't understand the importance to utilise kuzushi, as the neck is vulnerable to aggressive headlocks. I've found when they use kuzushi with koshi guruma uchikomi, there is no pain or nausea. Conversely, in nagekomi, headlock throws (e.g koshi guruma) do no hurt for me. Koshi guruma in randori would be difficult,if you do not use kuzushi to pull uke off balance or rotate fully to commit to the throw, or you could headlock partner & muscle them over, using strength, but there is the risk of injury to the neck. For me, neck based throws are either safe or unsafe depending on whether tori uses kuzushi & rotates properly to throw.
If they rotate properly with the throw, you're more likely to land on your back so you can breakfall, or you may fall badly, if they don't use kuzushi & turn properly. If tori lands on uke completing the throw, it is more dangerous if there wasn't kuzushi (more likely to land on your head, as throw may not be completed fully). Additionally, I've never done kubi nage, although I probably should have learnt it, however my neck would likely get hurt being thrown in it, as it is still bad from being headlocked in koshi guruma, like my neck became hypermobile from the whiplash,& now headlocks can make it spasm & lock up.
Kubi nage sort of reminds me of either harai makikomi or soto makikomi, but with a neck grip as it seems like a heavyweight throw, done when someone can't get kuzushi or lift uke's weight, so they muscle them over instead, & they're more likely to fall on you.
Overall, in my opinion, koshi guruma is unsafe in uchikomi (e.g whiplash if they whack you around neck & forget to use kuzushi).
In nagekomi or randori, kubi nage would be more dangerous as it seems to be a throw that uses both weight & momentum to pull uke over instead of throwing them over hip, e.g koshi guruma. It also depends on whether they are experienced enough to practice neck throws safely, neck throws in uchikomi can make me have pain in my neck & nausea, if they rush & I get whacked around my head instead of being pulled off balance.