You can get the electronic ones to replace the thermal ones but you won't get the hanging blinker when you lose a brake light or front turn signal bulb. Also, if you put a quiet one in, instead of a noisy-clicky one, you wont hear it clicking loudly to remind you that the signal is still on. Thermal ones are rated by load for number of bulbs controlled.
Electronic ones will work with a timed flash not caring of you have 3 or 6 bulbs so they are a better flasher.
Square or round, a flasher is a flasher.