Why ADC Differential Driver feedback resistors are small in hundreds range?
It really depends on the speed and what you intend to do

High speed signals need to be impedance matched, at higher speeds pcb traces start to act like transmission lines and there can be reflections if these are not matched. This probably doesn't apply as much in your case, but you need to be aware of it, especially in the PCB design.

The second thing is noise, you will increase the noise by increasing the resistance, but your also cutting down bandwidth at the same time. So you still end up with more noise at the end of the day.


The third thing is parasitics. Each pin and PCB trace has pF's of capacitance which can cause common mode issues and bandwidth problems. If you double your resistance, you are going to cut your bandwidth in half. You can also see this in the table above.

It depends on if these trade offs are acceptable for your design. You'll trade resistance for noise and bandwidth.

Here is some more info on diff amps and you should probably read the datasheet
You probably aren't going to be able to put 10k's in but maybe 2k's. The nice thing is this is easy to try, change the resistors and measure the noise.