I think you have a good plan to focus on grade and exams.
One more thought about colleges- make a list of the attributes of what you like about your dream schools.
Think Princeton has beautiful campus buildings? Look at Lehigh.
Like a school with a ton of clubs and activities? Don’t discount the big public flagships.
When the time comes to start thinking about the “why us” type of essays, I have some suggestions -
Look up the mission and vision statement for the schools on your list. Look at value statements. Some school also make their strategic plans public.
Research the four year plan of study for your intended major. There can be a lot of variability in gen ed requirements.
Read the schools’ student newspapers.
Look at the first destination surveys to see where new grads go to work, percentage that go grad school, etc…
Do a deeper dive on the type of research is being done by professors in your intended major.
That’s where you can start pulling fodder for your “why us” essays.