How many cores do the comparisons have? What is the test testing? The Intel has 14 cores that’s almost double and runs at 4.9 GHz. Of course if it’s single core testing it doesn’t matter how many total cores.

However that being said it all depends on the tasks you want to do. Apple software is written to take advantage is apple silicon so it’s designed to work better on those CPUs.

Comparing to a windows CPU isn’t really valid in the end.

Ifixit might have both battery and video on how to replace.

To be honest apple isn’t stupid they didn’t make a very expensive laptop that won’t their applications. You might find trouble with 3rd party apps, but even then it’s multi tasking that will be the issue. From reviews I’ve seen the 8gb is probably enough for most use cases and from the sound of it you aren’t going heavy load at this stage. Also as a student you have that most valuable resource - time. If things take longer or you can only do one thing at a time, so be it! Enjoy your new machine and stop looking at reviews or opinions on base M3 and 8 Gb.