Re: SubPac Realizations; Is there a "sweet-spot" frequency?
No, there is no "best" frequency. All sounds have their own sweetspots, due to timbre, harmonics/overtones, resonances, pitch envelope of a sound, proximity, etc.
Subs are generally 20-90Hz and they are omni-directional to the human ear. We have internal organs which resonates at lower frequencies, hence we "feel bass in the chest/stomach". Due to the power difference of highs vs. lows (as well as different resonances in/on our bodies) we need alot more SPL loudness to "feel" bass and sub bass (see Fletcher-Munson curve, or better yet the Robinson-Dadson curve).
Most basses and sub basses in today's music are very clear. There isn't alot of masking and overlapping in the low-end. A bass has plenty of room down there. This is usually why the bass seems so clean/controlled/loud/whatever.
When sound designing you can filter out the lows in most layers, to make room for a dedicated bass to take up the bass-seat.