Looking at the OPS you posted, I think Bloom's best move so far was bringing back Cora. He has all his veteran core performing again at the top of their games.
The four best regulars are basically pre-Bloom -- that is, if we swap back Verdugo for Betts (which, despite the stats, no one will say would make the Sox a worse team). ERod, Eovaldi, and Barnes are arguably the biggest mound contributors.
Arroyo's been solid, but the rest of Bloom's acquisitions have been so-so at best. The best we can say is they're versatile (so were Holt and Nunez in '18 -- decent, but not indispensable). Pivetta's been ok, and we'd be happy with '18 Porcello good for the season. New bullpen pieces like Otto, Hiro and Andriese have been mostly good, though maybe not yet comparable to the title trio of Kimbrel, Kelly and Hembree.
But without a doubt, Bloom's key get -- the gem of his tenure in Boston right now -- was stealing Whitlock from our arch-rivals.