I'll use it mainly for word processing, web surfing, giving presentations to classes, online teaching using Zoom, and some limited iMovie and Photo video editing.
I would say that with this pattern of activities, you will be safe with 8gb of RAM for following years.
My professor gets by old Air with 4Gb of RAM for the same activities with no hiccups.
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I think 512GB of storage is preferable. Why? Because on SSD drives you want to keep at least 30% empty for following reasons:
1) SSD will write many temp files and swap RAM, so if you leave it with free 10GB of storage, it will burn down a hole by writing/rewriting into that small space, which will cause eventually fail of the drive.
2) SSD speeds suffer a lot when full. So for max speed of the drive you need to keep 30% free.
30% of 512 = 358GB free for use to you.
30% of 256 = 179GB free for use only.
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You can watch a lot of videos on YT. You will realize that bigger storage is a feasible feature and you will enjoy it directly: for example by importing photos from your 128/256 GB iphone storage.
While 16GB of RAM is not easily feasible. Sometimes it will help you, sometimes you won't notice the difference between 8 and 16.
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On my current MBP 13, i feel cramped because of the space, rather than RAM. I am above average user.
I feel that 5% of the time, 8GB of RAM is limiting for me. 11-12GB would be good for my maximum load tasks.
While 100% of the time i feel my 128 GB storage limits me.
All in all, i am not ready to pay $200 for 16GB of RAM, which will help me only in 5% of the cases.