Shure SM7dB + Scarlett 2i2 4th Gen: which gain switch position?
Yes. At speaking level the SM7dB needs about 59 dB, and the Scarlett 2i2 4th Gen publishes 69, so 10 dB of gain is spare. Those are the published figures.
The Shure SM7dB has enough preamp on the Focusrite Scarlett 2i2 4th Gen for a normal speaking voice. You do not have to add a box in front of it.
Shure rates the SM7dB at -59.0 dBV/Pa, the voltage from a loud 94 dB tone at the grille. A speaking voice is closer to 85 dB, so the preamp still has to find about 59 dB to land near −9 dBV. That −9 dBV figure is just a tracking level: high enough to use, with space before the converter clips.
Set the knob for the voice you actually record and leave a little travel for plosives, instead of pinning it because the spec sheet has a higher number. A booster on a chain that already has about 10 dB spare only adds a box. Most of those boxes also use the phantom power themselves, which will silence a condenser.