These cars are in a perpetual Q&A state, they are getting modified between races. That's true for the "big teams", small teams don't have the resources, they're just "happy to be there". That's why it's possible to see stories like Brawn GP[^1]. That's what makes the sport fascinating, because the overtakes are not as much as one would hope for a ~2-3 hours race. But every little thing counts. In the last race 1st and 2nd had ~103ms diff or something like that for example, which is something that didn't happen for 15-20 years (maybe more).