Unfortunately, there's not really anything that can be done about the high latency inherent to geostationary satellite internet. Because of that latency, any type of VOIP service will always have a very noticeable delay. It can also cause problems with the functioning of the VOIP service, as in it not working properly, though system congestion can also add to this, and lately there can be a significant amount of said congestion because of so many more people being online than would normally be the case.
Regarding the YouTube, you can try turning off, or snoozing, the Video Data Saver, though with the resolution already being low it likely won't help much, if at all. That it's okay on your TV, but not on your phone, could be due to the app itself. You could also try alternating to the other WiFi band (5GHz vs 2.4GHz, and vice versa) with your phone, if it can, to see if that makes any difference.
You're very welcome. 🙂