What the mojo does is that it adjusts it’s volume to a line level setting, but does not actually bypass the amp. This might be a concern for some, but TBH it’s not going to cause a big problem in your system. I would personally still prefer the mojo as a dac to the modi, but that’s just me.
If you did decide to get a modi or whatever other dac, you would still have to hook up the source through USB or optical/spdif. You could get a dac that you could stream to if you were concerned about that