1. Olimar is view pretty well nowdays thanks to the efforts of Shuton. Outside of Shuton, Myran did okay but the Olimar representation is rather mediocre. Olimar has great potential though (Stickmen for example) and I would like to see other Olimar players breaking through tournaments outside of Shuton.
2. Sonic is pretty tricky. His weaknesses are not so noticable compared to Fox and Cloud (both have linear recoveries) and his strengths are kept strong. Imo, Sonic is going on a rise since KEN, Manny, Wrath, Ixis, and many others have placed well on tournaments. Sonic's MU is good against the latest backroom top tier but other characters above him can handle better. He can handle very well against Mario, Ryu, and maybe ZSS. He does well against Marth/Lucina too. His losing match-ups are Diddy, Sheik, Mewtwo, Fox, Rosalina, Bayonetta, and ESPECIALLY CLOUD. Otherwise, his representation and results grew more dominant thanks to KEN. However his results are not too dominant to compete against Fox and ZSS. Still...Sonic is on a right track.
3. Mewtwo is pretty good but I don't think he is top 5-8. He COULD be 9-12 but anything higher or lower than that is just ridiculous. Mewtwo's MU is good but similar to Sonic, it's not super-dominant. WaDi definetly helps the Mewtwo meta but recently he made a slight bump.
4. Meta Knight is more of a counter-pick character alongside DK and Bowser. However, MKLeo using MK much more and AC placing 9th at EVO Japan helps Meta Knight meta grow. Otherwise, potentially, top 15 is a likely and unlikely peak for him.