Well, the House is for representation by population. The Senate is designed to balance that power for the theoretically underrepresented smaller states, so that all have that equal representation. The problem is that the House--and therefore the larger states--are woefully underrepresented due to available seats based on population.
As it stands, the smallest states have vastly outsized power as it is. I see no issue with increasing whatever number of states that all citizens agree to, as well as increasing representation to an acceptable number that is more relevant to our current population instead of the current standard of, I dunno...~1893?
As for the SCOTUS, I agree with Biden's proposition, but I don't see any reason not to increase the number of the seats. It's already been done before and it isn't something that is that difficult to do. It currently represents yet another over-powered, over-represented body where the extreme minority of our country vastly outweighs something like what 90% of this country actually wants to be. It's wholly unsustainable. Likewise, the federal judiciary is woefully understaffed, by design of the GOP. We need something like 300 or more seats throughout the US, also with term limits and something like an actual experience/qualification standard to be offered a seat.
I'd rather not see any more justices appointed with the qualifications of: "Denny's picture menu reading level," and once said a very nice thing about an 78 year-old senile toddler man baby.