I have a zoom h4n and a rode stereo/video mic. I'm still getting used to audio. I wanted something I could put on my subject for interviews or something on myself to record speeches etc. where I can't have anything else around.

What is the best android app (I have no Apple devices) for recording using this lav?

Dumb question number 2: Does the way the H4n picks up audio via it's built-in mics work better or worse than say attaching the Stereo/Video mic instead?

Whichever mic is closer to the sound source is going to sound best.
I have no experience recording to 'iphones' or other phone type devices, but would surmise a decent quality lavaliere mic plugged into the Zoom would yield the most professional sounding result. The H4n inherently doesn't have very good microphone preamps, but I'm sure they're much better than any smartphone. Depends on your expectations of what sounds 'good'.

You could also try the iRig pre. I am told it works very well.

Whichever mic is closer to the sound source is going to sound best.
I have no experience recording to 'iphones' or other phone type devices, but would surmise a decent quality lavaliere mic plugged into the Zoom would yield the most professional sounding result. The H4n inherently doesn't have very good microphone preamps, but I'm sure they're much better than any smartphone. Depends on your expectations of what sounds 'good'.

Yeah, I figured that would be the case. It's just placing the H4n somewhere on the talent that's going to be difficult. If they're just sitting there then that's what I'll try.

Some use the affordable H1, it's pocket sized and will work with a most lavs w/ 3.5mm connectors.
Also likely to sound better than a smartphone and will record uncompressed PCM files (.wav).