  We propose and employ a novel empirical method for determining chromospheric
plage regions, which seems to better isolate plage from its surrounding regions
compared to other methods commonly used. We caution that isolating plage from
its immediate surroundings must be done with care in order to successfully
mitigate statistical biases that, for instance, can impact quantitative
comparisons between different chromospheric observables. Using this
methodology, our analysis suggests that 1.25 mm wavelength free-free emission
in plage regions observed with ALMA/Band6 may not form in the low chromosphere
as previously thought, but rather in the upper chromospheric parts of dynamic
plage features (such as spicules and other bright structures), i.e., near
geometric heights of transition region temperatures. We investigate the high
degree of similarity between chromospheric plage features observed in
ALMA/Band6 (at 1.25 mm wavelength) and IRIS/Si IV at 1393\r{A}. We also show
that IRIS/Mg II h and k is not as well correlated with ALMA/Band6 as was
previously thought, and we discuss the discrepancies with previous works.
Lastly, we report indications for chromospheric heating due to propagating
shocks supported by the ALMA/Band6 observations.
