Haven't seen No Way Home yet, so I defer to what others have said there. As for whether you need to see Eternals for other purposes, I'd highly recommend. There is likely no urgency to it, but the scope of that film and its future ramifications is likely as big as any MCU movie we've seen thus far, therefore whether you end up liking the movie or not, you really should probably see it. Shoot, I didn't even necessarily love the movie myself nor all its ramifications, but they are ramifications which will be felt in the MCU. Compare all this to a movie like Black Widow, which I liked and recommend people see it, but its scope and essentiality to watch in order to understand future movies is likely pretty low.