Finally made it to the end of this thread and i feel for ya on the problems you've experienced so far, there will be more along the way but with this forum and all the helpful people it will get easier to overcome, that being said i have a couple of answers for you i think lol.
you asked about the juices and them tasting differently as far as chemical/alcohol/plastic tastes some vendors use different means of diluting liquids and flavors, I've seen some people use alcohol's, distilled water, and just plain pg or vg, some flavors can give off different flavor notes (floral, candyish, menthol) among others, some juices may contain sweeteners and I'm unaware of what kind of taste that would give off because i don't think I've had any in mine (i mostly diy).
when i first started out i had the 510 slim batteries that resembled a cigarette and they worked for a while with lr single coils quite well for me but then i realized i was rotating batteries constantly so i looked for a bigger battery solution which led me to a vv boxmod that i put through hell and i dont know how many battery rotations with a Dual Coil Carto tank for the delivery system also running 1.5 ohm dual coil cartos with 3 holes punched. i now use a "monster mesh" (DID style Rebuildable genesis tank) on a VMAX which will last me 1 to 1 1/2 days on a single charge.
as many others have stated juice is a preference as far as what works for you, i love bobas bounty from Alien Visions (100% vg juice) and it worked quite well in my dct with 3 holes punched, ive had a few of the high caliber liquids you speak of and i ordered them from Altsmoke there were a couple that were alright as far as flavor for me but i found other vendors with better tasting juices that i like, recently ive tried halo's tribecca and midnight apple and they were both great, also pyramid fusion from Gotvapes is one of my new favorites along with Backwoods Brew's 555, i still dabble in the DIY but not near as much since ive found these vendors and im sure i will find many more along the way.
you asked about the juices and them tasting differently as far as chemical/alcohol/plastic tastes some vendors use different means of diluting liquids and flavors, I've seen some people use alcohol's, distilled water, and just plain pg or vg, some flavors can give off different flavor notes (floral, candyish, menthol) among others, some juices may contain sweeteners and I'm unaware of what kind of taste that would give off because i don't think I've had any in mine (i mostly diy).
when i first started out i had the 510 slim batteries that resembled a cigarette and they worked for a while with lr single coils quite well for me but then i realized i was rotating batteries constantly so i looked for a bigger battery solution which led me to a vv boxmod that i put through hell and i dont know how many battery rotations with a Dual Coil Carto tank for the delivery system also running 1.5 ohm dual coil cartos with 3 holes punched. i now use a "monster mesh" (DID style Rebuildable genesis tank) on a VMAX which will last me 1 to 1 1/2 days on a single charge.
as many others have stated juice is a preference as far as what works for you, i love bobas bounty from Alien Visions (100% vg juice) and it worked quite well in my dct with 3 holes punched, ive had a few of the high caliber liquids you speak of and i ordered them from Altsmoke there were a couple that were alright as far as flavor for me but i found other vendors with better tasting juices that i like, recently ive tried halo's tribecca and midnight apple and they were both great, also pyramid fusion from Gotvapes is one of my new favorites along with Backwoods Brew's 555, i still dabble in the DIY but not near as much since ive found these vendors and im sure i will find many more along the way.