I've never gotten excellent deep flavor from a pen.
There are a few great RDA/RTAs on the market for flavor, but it's equally important to have the proper build, airflow setting, and voltage/wattage.
For a simple starter setup just to learn, you might consider a single coil higher ohm build. Wattage set between 45-65, and a more restricted airflow. Too much airflow tends to dilute the density of flavor.
I am strictly a flavor chaser. I do not care if I see one iota of vapor. I'm waiting on 6 new RDA/RTAs for flavor builds so I am currently using the Aromamizer Supreme and the Limitless Plus. More PG equals better flavor but too much PG equals too harsh a throat hit, as does too much nicotine. A 3mg nicotine and either 70/30 or 60/40 VG/PG ratio will give substantially more flavor than a max VG mix. Too much nicotine will cause a harsher, more peppery taste. Too much VG will mute your flavors. Too much airflow will do the same.
Some of the better reviewed RDA/RTAs for flavor: Hobo, Kayfun V5, Genesis, Le Magister, Rose V3.
These are all a tad more difficult to build than your standard velocity deck with only a few pieces to clean. Many have tons of pieces and more difficult wicking, but nothing a few YouTube videos can't walk you through.
Higher ohm builds yield more flavor in my opinion. The minimum I like for flavor is .4 but the sweet spot for me is anything closer to 2. Single Coil builds are the easiest way to get there. Tensioned coils helps with proper heating. Wicking also matters a great deal. I prefer a Fiber which has visibly long strands.
Flavor can be changed by the material used for your coils. Some people notice difference nuances with different metals. SS316L is a popular coil with a general consensus of zero taste.
This is all just my opinion. Taste is nearly completely subjective but many of these guidelines have worked for a lot of people. I'm no expert, just a person who has done a lot of research, trial and error.
You do get what you pay for quite often with juice. Premium juices do have better flavors as a general rule. House blended juice is often weak with a mild overtone of flavor. Juices like Dinner Lady or Cassadega will make you feel like you've just stuffed your face with actual foods. Quality liquid will not have the harshness or chemical, perfume taste of inexpensive or fresh juices. There are some cheap juices on the market that are minimally acceptable after a very long time steeping but I want to feel like I've got a mouthful of food.
Again, these are purely personal observations. YMMV.
