Will these 100 ohm resistors protect my GPIOs from power surges?
Assuming that you mean ESD (electrostatic discharge), then - NO. There are special diodes called &quot;Transil&quot; which suppress transient voltage spikes. (almost) All modern microcontrollers have diodes on input for input protection, so unless you want to protect chip from serious, high energy ESD discharges (like in human body model), than you don't need additional protection.
Assuming that you mean long line driving with digital signal- YES, that will limit surge current. BUT - this will also increase line charging time and spoil shape of your signal.