Welcome to the forum!
I think we might need to gather some more info, before I can answer. Path menu > Object to Path won't work on a JPG. You'd have to first convert the JPG to a vector graphic by tracing, whether "manually" or using a trace engine.
What do you mean when you say the bows and curves are not round. Do you mean they look round at 100%, but when you zoom in, you see that the curves are made of many straight segments?
If they really are JPGs, you won't be able to fix them until they are converted to vector. And that process might just fix those straight segments. But if you already did convert the JPG to vector, we can tell you how to make them into curves.
The fastest way to answer all these questions, and get to the info you need, would be if you could provide the SVG file that you're working on. You could either attach it to your next message, or just upload wherever you like, and give us the link to it. To attach to a message, do not use Quick Reply, and instead look for the Reply button. (It can be found either just above your first message, or just below the last message in the thread, in a row of a few buttons.) Once there, you'll see a link for attachments just below the message box.
