Great advice from @Timwis and @Spink .
I often use squonk mods for RTAs. Any salesman who tells new vapers that this is not possible is either stupid or purely sales-driven. Another advantage of using a squonk mod is that you can use the juice compartment as a space to carry a refill for your RTA.
Your main issue seems to be getting the best flavour.
Have you ever considered that you may be taste challenged? Not an insult I assure you. I have difficulty in identifying certain flavours. At the last vape meet, a friend of mine gave me a juice to try. Believe it or not, I thought that it was tobacco when in fact it was some type of fruit mix. Do yourself a favour and do a bit of research on how humans experience taste and smell. Approximately 25 % of us are non-tasters, 50 % are medium tasters, and 25 % are "supertasters."
If, like me, you have taste issues, you will always be searching for something that is unattainable. I have found what I like and DIY to suit my tasting abilities. I have lowered my expectations. I know that I will never be able to identify all the flavours in a complex juice. I should mention that before vaping I had no idea that I was taste challenged.
Good luck with your journey.
Sometimes I can identify different flavours in coffee juice, but in fruits, which I don't often vape, not at all - just an overall sense which I classify as "Like" or "Dislike"!