I use the comm tools in Roll20 with voice only. We have very few problems with a group of seven. I have had more issues with voice on discord than on Roll20. I have never used video.
The groups I have played with always go with Roll20, but with Discord for audio. I don't think it is an improvement. When we play with just Roll20 - only using the audio component and no video, like ImaginosMusic, we will have a few drop-outs (where someone can't hear someone else) but they are generally cleared up by reconnecting. That only takes a few seconds, usually. On Discord there have been several times where a person will be dropped and cannot reconnect at all. It is texting for them for the rest of the game. So, my - admittedly limited - experience is to just use one platform, don't cross the streams (so to speak
).
I have no experience at all with Astral. (I am wondering if you are talking about using Astral Space to communicate through. I mean, what is wrong with the Ethereal Plane? Not good enough for you, huh?!?!?
)