Since the present Congress is dominated by Democrats, Biden would be President for all intents and purposes until such time as Congress acts.
That would mean that Biden's signature would be adequate to make legislation into law. Though there might be an asterisk by his name, Biden would be the next President in the history books. An "acting President" is a President. He is one who is authorized to preside and act.
Congress is only dominated by Donks for a few more months, though.