  The carbon-to-oxygen (C/O) ratio in an exoplanet atmosphere has been
suggested as a potential diagnostic of planet formation. Now that a number of
exoplanets have measured C/O ratios, it is possible to examine this diagnostic
at a population level. Here, we present an analysis of currently measured C/O
ratios of directly imaged and transit/eclipse planets. First, we derive
atmospheric parameters for the substellar companion HD 284149 AB b using data
taken with the OSIRIS integral field spectrograph at the W.M. Keck Observatory
and report two non-detections from our ongoing imaging spectroscopy survey with
Keck/OSIRIS. We find an effective temperature of $T_\mathrm{eff} = 2502$ K,
with a range of 2291-2624 K, $\log g=4.52$, with a range of 4.38-4.91, and
[M/H] = 0.37, with a range of 0.10-0.55. We derive a C/O of
0.59$^{+0.15}_{-0.30}$ for HD 284149 AB b. We add this measurement to the list
of C/O ratios for directly imaged planets and compare them with those from a
sample of transit/eclipse planets. We also derive the first dynamical mass
estimate for HD 284149 AB b, finding a mass of $\sim$28 $M_\mathrm{Jup}$. There
is a trend in C/O ratio with companion mass ($M_{\mathrm{Jup}}$), with a break
seen around 4$M_{\mathrm{Jup}}$. We run a Kolmogorov-Smirnov and an
Anderson-Darling test on planets above and below this mass boundary, and find
that they are two distinct populations. This could be additional evidence of
two distinct populations possibly having two different formation pathways, with
companion mass as an indicator of most likely formation scenario.
