AE can scale vector graphics, if the scale goes above 100%, use the ‘continuously rasterize’ switch, the little star next to shy guy. this will enable scaling above 100%.
Shape layers are vector layers so should scale up no issue.
maybe theres a script that could globally turn these switches on, i dont know though!
How are you scaling up each comp? I would make the comp 4k, then add a null and parent all layers to it, then 200% it, unparent and delete null. But that depends on any other parenting you have going on.