That's exactly correct, the XLR out is mic level and the 1/4" out is somewhere between instrument and line level, depending on the input level feeding the box and where you set the output volume. The finally has a pre out switch which allow you to bypass the tube pre and have a dry signal unaffected in the 1/4" output.
I just used my finally for a full month of shows and it worked like a charm. I installed a 12AU7 in mine to get more, clean tube input gain before it saturates into overdrive.
For me, the stock 12AX7's gain was too "hot" and it was either too much or not enough gain, I couldn't find a sweet spot, the AU7 fixed it. When I first used it with the stock 12AX7 the sound guy told me that last thing he wants is hearing a DI box distort.
I'm feeding the output of my pedalboard into a Morley optical volume pedal then into the finally's input and taking the 1/4" out of the finally into my amp. That way I can control my volume and dynamics in the pit and into the house alike, and it allows me to mute myself when changing basses without having to use the tuner as a mute.
After years of recording and live, I decided, long ago, that I knew my sound better than most engineers, so I send them a solid, eq'd, fx'd, and compressed feed and I tell the engineer to get his maximum gain level, set the board EQ flat and I'll take it from there. Once they hear it, they love it, and the fact I'm one less thing they have to worry about during the gig.
I'm totally pleased with my finally and it really enhances my overall tone, it just takes some time set it up.
How hard it is to switch tubes? I actually have an AU7 I was going to put in a guitar amp but never did. I don’t mess around opening electronics too often so am a little hesitant to try. Does it sound a lot different?