Question about the implications behind “私でよければ“ Does is contain any romantic implications? I’ve heard it can be used as a love confession or marriage proposal of some sort, but is that true? And is that a common phrase? Thanks!

All by itself without context, {} _**does not**_ contain romantic implications. How could it? In fact, when I read your question, I murmured to myself {}, roughly meaning " _ **If it's OK with you, I**_ would post an answer."

simply means "If it is OK (with you), I ~~"

Even in a romantic context, all by itself does not really mean much. It is not a complete sentence in the first place. You might use it in complete sentences such as:

> {}{} ("If it is OK wih you, please date me.")
>
> {} ("If you find me acceptable, please marry me.")

is an _**extremely**_ common phrase in all kinds of situations. It makes you sound humble and not pushy/aggressive/impolite, etc.