Julia is one of those girls who in the morning prefers slow and gentle cuddlesex. Her favorite position is to be sat in your lap as you move her up and down so she can kiss your face and bury her face in your chest, she loves the feeling of having you wrapped around her. However, at night Julia prefers to be railed pretty hard, going from God is watching to OH GOD!!! . The exact position wouldn't matter to her, so long as you're hitting her sweet spots and she can bury her face in a pillow, she's happy. She's also very susceptible to being teased during sex. Julia may have weird fetishes. But for her, a weird fetish is something like armpit licking, which in my house is vanilla. What she definitely does have is an intense praise kink. A few well placed "good girl"s is enough to break through any resistance to anything she may have. Importantly, Julia has an average (possibly slightly below average) sexual stamina. Meaning she'd get tired somewhat easily. However, because she's such a sweetheart (and because little sisters always want to appear grown) she tries really hard to please her lover. If it's a birthday or special occasion, she would ask you to do whatever you want to her and that she'll do her best to endure, because today is about you. She also enjoys giving blowjobs, but it embarrasses her to admit this.
Overall, I believe sex with Julia would be pretty good if you're a strong man, physically and sexually. Julia would essentially let you ravage her while also doing almost whatever you ask.
About Ashley, it's important to start with the fact that Ashley wouldn't be a dom. A true female dom is extremely rare, again because of sexual dichotomy (I had a rant here about findoms which I had to cut out). How Ashley's particular enthusiasm would manifest is as a very high sex drive and a desire to be extremely active in bed. It's important to separate drive from stamina. Ashley is still a pure maiden, so at the start she would have normally low stamina. But over time as her stamina grew, she'd start moving a lot more on her own. Gyrating her hips against yours with her own rhythm, making small positional adjustments, etc. After her stamina builds up, she'd probably enjoy riding you a whole lot. Other than riding, no particular positions jump out at me. Again, I think so long as you're hitting her sweet spots then she's happy. I do think that Ashley would want an eclectic mix of being railed and cuddlesex 24/7, regardless of what time of day it was. I have a hard time working out her embarrassment. I think initially she'd be very put off at having her love returned honestly. But after getting over that, I think she'd smile and giggle a lot during sex just due to the euphoria. As for fetishes, incest is vanilla around here so I shouldn't even mention it. Other than that, I don't really know. If she's having sex with you, I think she'd be down to try anything.
Overall, sex with Ashley would determine entirely on how well you and her sync up. If you're on the same wavelength (like her and Andrew would be) it would be very good, since you'd both being dancing in step. However, if you're out of sync with her, there could be some issues.
Also, I know I used the second person in this post, but obviously I'm assuming the reader is Andrew