  We determine the physical properties of a sample of SMGs in the COSMOS field
that were pre-selected at the observed wavelength of $\lambda_{\rm obs}=1.1$
mm, and followed up at $\lambda_{\rm obs}=1.3$ mm with ALMA. We used MAGPHYS to
fit the panchromatic (ultraviolet to radio) SEDs of 124 of the target SMGs,
19.4% of which are spectroscopically confirmed. The SED analysis was
complemented by estimating the gas masses of the SMGs by using the
$\lambda_{\rm obs}=1.3$ mm emission as a tracer of the molecular gas. The
sample median and 16th-84th percentile ranges of the stellar masses, SFRs, dust
temperatures, and dust and gas masses were derived to be $\log(M_{\star}/{\rm
M}_{\odot})=11.09^{+0.41}_{-0.53}$, ${\rm SFR}=402^{+661}_{-233}$ ${\rm
M}_{\odot}~{\rm yr}^{-1}$, $T_{\rm dust}=39.7^{+9.7}_{-7.4}$ K, $\log(M_{\rm
dust}/{\rm M}_{\odot})=9.01^{+0.20}_{-0.31}$, and $\log(M_{\rm gas}/{\rm
M}_{\odot})=11.34^{+0.20}_{-0.23}$, respectively. The median gas-to-dust ratio
and gas fraction were found to be $120^{+73}_{-30}$ and $0.62^{+0.27}_{-0.23}$,
respectively. We found that 57.3% of our SMGs populate the main sequence (MS)
of star-forming galaxies, while 41.9% of the sources lie above the MS by a
factor of >3 (one source lies below the MS). The largest 3 GHz radio sizes are
found among the MS sources. Those SMGs that appear irregular in the rest-frame
UV are predominantly starbursts, while the MS SMGs are mostly disk-like. The
larger radio-emitting sizes of the MS SMGs compared to starbursts is a likely
indication of their more widespread, less intense star formation. The irregular
UV morphologies of the starburst SMGs are likely to echo their merger nature.
Our results suggest that the transition from high-$z$ SMGs to local ellipticals
via compact, quiescent galaxies (cQGs) at $z \sim 2$ might not be universal,
and the latter population might also descend from the so-called blue nuggets.
