Cloudlifters are very overhyped (so are sm7s) although I do own the one with impedance knob.
Let's begin with no cl...
Set the Tascam mixer chnl input fader about halfway up, connect your sm7 & if you can hear it ok against your other overdubs/monitoring, my vote is don't buy a cloudlifter.
It's especially not necessary if your normal procedure is to move the tracks to computer daw....where you can normalize after-the-fact to position daw faders in good relative gainstaged positions to each other.
On the other hand, if everything you do is in the Tascam and stays in the Tascam....and you find you really have to crank the 12s fader way up to hear the sm7, perhaps a cl investment will be your preference. Then, you can run the 12's fader lower, which theoretically places the channel in a better s/n range.
I don't like the sm7 myself. Unless you're eating the mic (in which case a 57/58/re20/441 are much better to sing into imo), the sm7b just simply picks up too much crud around the room....which is amplified (by the way) if you introduce a cl and insist on singing more than 2" off the mic.
I bought the Cloudlifter-Z mainly to experiment with shifting the impedance knob on 57s, ribbons, re20 etc to experience what happens when tracking....which is pretty much pretty subtle.
It is nice to have pre-gain for dynamic/ribbons, but again, you can simply normalize in a daw.
It's your call.