The first and most obvious answer is that middle-class tax brackets would go up. Middle-class families by and large fall into the 12%, the 22%, or the 24% tax rates on the margin (that is, on their last dollar subject to income tax). If Biden gets his way, these tax brackets would rise to 15%, 25%, and 28% (respectively).
https://www.washingtonexaminer.com/opinion/if-youre-in-the-middle-class-joe-biden-wants-to-raise-your-taxes
The 28% the Obama plan had included deduction of mortgage interest: https://www.fool.com/taxes/2013/04/11/how-the-obama-budget-would-change-your-taxes.aspx
The first and most obvious answer is that middle-class tax brackets would go up. Middle-class families by and large fall into the 12%, the 22%, or the 24% tax rates on the margin (that is, on their last dollar subject to income tax). If Biden gets his way, these tax brackets would rise to 15%, 25%, and 28% (respectively). https://www.washingtonexaminer.com/opinion/if-youre-in-the-middle-class-joe-biden-wants-to-raise-your-taxes
That equates to about $1,500 a year at 50k there.
This fact checker said the tax brackets wouldn't change https://checkyourfact.com/2020/10/16/fact-check-joe-biden-federal-property-tax-increase/, so now you have to decide if this "fact checker" who has no expertise in the area of taxes https://twitter.com/AtienzaElias or this guy who does have tax bonafides: https://twitter.com/ryanlellis is correct.
And as far as the claim about the Social Security part, that's true. Even left-wing Snopes agrees that it's true: https://www.snopes.com/fact-check/biden-tax-social-security-1983/