Since you're driving it faster in 2-3 days, you definitely want I-70 on the initial route from Kansas City (Kansas)
through St. Louis
Once you hit Columbus, the question is whether to continue on I-70 to Pittsburgh
or link up to I-90 in the north.
If you stay on I-70 on the southern route and try I-76 into Philadelphia
, then I think you may be slower connecting back north going through New York City
So maybe it does make sense to take either I-80 or I-90, stay north of NYC, perhaps maybe Niagara Falls
a side trip if you have 3 days and you want an extra stop, then pretty much head to Boston