So basically last night I finally started doing my E3D conversion and also decided to upgrade my extruder hence I never been entirely happy with it.
Everything at the moment is hooked up but no cable management or so been done so far.
Still trying to figure out the best way to organise things.

Anyway.
Question is about the sensors.
1. Sensor in hotend head which senses filament presence.
2. The same filament presence sensor in extruder box.
3. Rotary encoder in extruder box.

1. So far I figured out that sensor only matters when changing spool. If sensor can't sense filament it keeps extruder. Doesn't matters while printing or so.
2. I've even unplugged it and was able to print with no problems. Actually I was hoping it will pause the print or so, Anthem's  idea to use it as "run out" filament sensor made me think that I could use it with stock firmware.
Actually I haven't tried to change filament, will try tonight.
3. I'm clueless what it does. As per old forum posts it's not responsible for any filament used counting. Also doesn't matter  when it's unplugged. Does it do some kind of a feed correction?! Doubt it hence there's no difference printing with or without it.
Maybe it was disabled in latest firmwares because it didn't worked or so. I'm clueless as I said.

Does anyone has any input or better knowledge of those things?!

Regards,
Kris M