Does choosing to help Chole affect the path with Isabel? And does telling Riley the truth do anything?
As far as I can recall:
1) Helping Chloe puts you on the path of wanting to get away from the drug life as soon as you can, while manipulating her makes your character want to keep going with the business. The way that this affects Isabel is the same, as she'll think and support whatever your MC chooses. So, if MC wants to stop being involved, so will she; but, if he wants to keep earning money, she'll have your back as well, as that money can be important to help her grandma. Either way, helping or manipulating Chloe doesn't change your romantic involvement with Isabel, at least so far.
2) Regarding telling the truth to Riley or hiding it from her, the biggest difference as of now is Elizabeth, especially considering the events of chapter 8. Without delving too much into spoilers, you can get involved with her in this episode, but depending on whether she knows you're in the drug business or not the scene and how she behaves towards you will change.