Welcome to the V40-owners club
Other than the slightly large size and poorer battery life (compared to the V30), I also think it's a pretty nice phone. BTW, I also own the ER4XR. Their impedance is just slightly too low to trigger high-impedance mode on the V40, so you might want to try the adapter trick (in the 2nd link below) to get more headroom.
I wasn't the biggest fan of the Mojo, mainly because of its poor shielding (which might explain why you prefer the N3 as a transport?). Just playing Devil's advocate on a couple of other points here...
Mojo doesn't measure nearly as well as the V40 in terms of signal over noise and distortion (look on the list for the G7, which shares the exact same DAC/amp):
https://www.audiosciencereview.com/...ad-distortion-comparison-graph-for-dacs.4814/
That's not to say you shouldn't prefer something that, in some formal sense, doesn't measure as well. I have plenty of gear that measures like crap but sounds amazing. I'm afraid I can't explain that, so if you really like the sound of the Mojo, then that's obviously the right answer for you. But the other point is whether you're really playing your files back bit-perfect in UAPP. Appropriate settings are explained here:
https://www.head-fi.org/threads/music-apps-tips-and-tricks-for-the-lg-v30.868978/
However, if your V40 is running Android Pie, all bets are off unless you're running a permanent dumpsys of audio_flinger to confirm the sample rate of every single track. There's one individual on this thread who got very excited about seeing an audio_flinger output showing the correct sample rate and assumed that one anecdotal example proves there isn't any problem with Android Pie. I can promise you they're wrong. All music apps on the V40 (even LG's own music app) are having issues with PCM files when switching sample rates in Android 9. You may indeed have been listening bit-perfect with UAPP. But if you're on Android 9 (Pie), there's also a good chance you weren't. (There is a work-around for UAPP on the horizon, but nobody outside of myself and the UAPP dev currently has that.) It's not an ideal solution, but if you manually set the correct sample rate in Poweramp, that is consistently playing back all PCM files correctly on the V40.