Hi Redbeard
I'm a relative newbie too and just happened to be looking up info on that popping of the coil 2 days ago. The general answers I found were that it is simply part of vaping and you will get used to it. I was looking because I have an RDA (a rebuildable drip atomizer) and I was wondering if the popping had something to do with the way I had wicked it or not. One person suggested it may have something to do with the tightness of the cotton through the coil but they were the only one to say this. It's not relevant anyway to premade coils so I guess the answer is "it happens" when it comes to popping of the juice.
That said it can be made worse if the coil's being flooded with juice. I often find if I leave my vape for any amount of time the coils begin to get flooded and the first vape is often gurgly, wet, spits, and pops. I often have to clear the coil by blowing through the atomizer while holding the fire button. That clears the excess juice and the next vape is better.
Some juices seem to pop more than others, it probably has a lot to do with their viscosity. I find that when switching juices the power setting often has to be changed even when they are supposedly the same ingredients in the juice except for flavoring. Of course maybe that's just me since variable power settings can and does produce different vape experiences. Your Endura however is working with a fixed 14 watt setting so you can't change any power settings. I believe though that that sort of system the charge level of the battery will effect the amount of power being sent through the coil so you may find it vapes quicker and hotter on a full charge than otherwise.
You mention a burnt taste. That usually happens when the coil runs a bit dry of juice, a dry hit. That can happen if you are chain vaping and not giving the unit enough time between vapes to wick more liquid to the coil. It can also happen when you switch to a thicker juice (higher in VG than PG) as the thicker juice takes longer to wick. Also important to properly prime the coil for first time use. The burnt taste is the cotton in the wick actually burning because it dosen't have enough juice on it. If you burn it badly enough the burnt taste will linger and you'll have to change your coil. A quick taste of burning and usually your coil is still fine.
Good luck with it and keep experimenting, it's lots of fun and about the only way to get good at this. At least eventually I hope to get good at it.
Steve