ART Tube MP Studio V3 with an Elgato Wave DX: ART's own sheet says 50–60 dB, the shops say 70 or 80
Yes. With the Tube MP Studio V3 already in line, the MiniFuse 2 only has to supply about 0 dB of the 56 it publishes. Those are the published figures.
The hard gain is already done. The ART Tube MP Studio V3 sits in front of the Arturia MiniFuse 2, so the interface preamp is no longer the thing that has to rescue a quiet microphone.
Elgato rates the Wave DX at -52.0 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 0 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.
Feed the interface from the booster's output and do not stack a second microphone preamp on top. Most inline boosters spend the 48 V themselves. That is fine for a dynamic. If this microphone is a condenser, read the booster's manual before you leave it in the chain: if it does not pass phantom, the capsule goes silent.