I’m studying some minor harmony and I’ve done this little exercise with all chords in root position

My question is: since In a minor setting you have multiple choices about triads (whether you are considering melodic/harmonic/natural minor), are you basically free to choose which triad to use (from a specific scale?)
For example in 3.4 I start with C minor triad, then I go for Eb augmented triad (considering the melodic minor ascending) and then I go for F minor considering the natural minor (having the flat sixth).
So is it possible to switch between melodic/harmonic/natural choices?
(I still have to do the 3.5)