I don’t believe there is any harm in creating a profile on these online platforms before being funded. But in my experience you are not likely to get much traction with investors there unless you first: (1) have a lead investor you have met with in person who is in for 5% to 10% of your round; or (2) have established connections with investors who can promote your deal on these platforms. Investors want to see some kind of preliminary due diligence on you and your deal before they commit.