I have joined both pluspora and mewe.

I have joined both pluspora and mewe. Because the pluspora "pod" has recently and suddenly been flooded with G+ refugees, I would say the overall quality of posters and content there is excellent. The "stream" is everything anyone posts, and not the sort of thing you'd likely follow in the long term - as a few thousand G+ folks have arrived in the past day the "stream" is filling with purveyors of their photographic efforts (not a major focus of mine), and memes; but it is possible both to follow individuals like a circle, and hashtags marking topics; and thus avoid the uninteresting bits. A group could choose their own obscure hashtag and exchange posts that would not come to the attention of most users unaware of the hashtag (though all their posts would be viewable by anyone in the main stream). The community is too small to attract spam so far. Pluspora is part of a larger diaspora.org project and there are other pods. One can add contacts from other pods and thus see broader content; some of which is on par with what I have found on G+. I find that encouraging.

The mewe community is a bunch of groups all in one basket - one server I think. It seems to be long-established, but of lower content quality (a bunch of nut-jobs, imho). The entire content is contained in groups, so you would only follow groups of interest and never see the content of the other groups. That would be a good thing if G+ emigrees were to flood the community with a surge of quality, but quality content is not something you can go and tap into today - rather, something that would have to be built one user at a time. Mewe groups have an administrator and they can be open membership or by application - I have not seen mention of moderator positions within the couple of groups I visited.