I want to talk for a minute about thumbpicks. They're all different, with different sound, pitch, size, etc. depending on what you want. My current favorite is one called a Golden Gate thumbpick, but they seem to be all different! The only one who can get it right is my buddy Johnny Hiland, who seems to know exactly what I like and gives them to me. Golden Gate makes a thick pick, but I also use some that are thinner and others that have a longer base.
Watching a lot of the young players, I see that they push the pick clear up their thumbs past the nail bed. I personally can't play like that, but experiment and see if it works for you. Travis put the thumbpick on about half-way down his nail, and slightly turns it in so it's at an angle when it hits the string, changing the sound.
One of the things about playing with a thumbpick, is that it doesn't often sound good in the studio. That is until Fred Kelly came around and made a "speed pick", which is a little flimsy, making it sound like you're just playing rhythm guitar.
If you're looking for something pretty, don't use a pick at all for a softer sound! You can also change up where you're playing on the guitar - closer or further from the bridge - to get a softer or twangier sound. Merle Travis would play something like a single string line up on the neck to make it sound softer. If you've seen Travis play his big Gibson Super 400 Special, you'd see the long whammy bar with a ring on the end. He'd hook his finger in the ring, going even further up the neck to get that bell like sound.
Chet Atkins preferred the blue Herco picks, as does Brent Mason. Jerry Reed preferred a harder pick, but he'd play a nylon string. This led people to think he played really hard, but he was actually very delicate. He also had his strings almost at the neck, so he didn't have to press down at all to play them. Chet on the other hand wanted the strings far off the neck, which he makes look easy! Personally, the action on my guitars is very low.
However, nobody says you have to be me, Merle Travis, or Jerry Reed, and I promise that you're not Chet! You're you, and music is just an expression of yourself. Tell the story your way, grin, and somebody will probably like it! Get yourself a thumbpick and experiment.