I'm not saying fWAR should decide which Sox team was the best, but here are some numbers from 2004-2018:
Best fWAR (batting + fielding)
36.3 2011
36.2 2013
35.2 2016
32.9 2008
32.2 2018
29.7 2007
27.6 2005
24.9 2010
24.7 2004
24.4 2009
(wRC+: 117 in 2011, 114 in 2013 & 2004, 113 in 2016, 112 in 2005, 111 in 2018, 110 in 2008 and 109 in 2007 & 2010.)
Pitching fWAR:
23.2 2017
20.6 2004
18.8 2016
18.5 2018 & 2009
18.4 2007 & 2008
15.8 2013
15.7 2010
Add together:
52.0 2013
50.7 2018
48.1 2007
45.3 2004 (Best pitching)