I strongly concur with my esteemed colleague from west of St. Louis
The vast majority of LORs are strong/positive. However, the top/outstanding letters are:
1) not simply letters of recommendation but well written letters of evaluation (which is the official name)
2) they show evidence of both time and depth of relationship for the writer and the applicant
3) the writer evaluates based in their own experience and interaction of the applicant
4) they discuss the traits, characteristics and attributes of the applicant
5) they give examples of the above
6) they place the student/activities in context compared to other students they have taught, etc
When you request a letter you should
1) outline your history, interactions, relationship with writer
2) provide suggestions of what characteristics, traits, attributes you think your work/interactions demonstrate about yourself
3) Always attach and link (yes do both) the AAMC writers guide; they will appreciate having guide laid out them
4) Ask early enough and followup to make sure you get the letter
5) Letters are processed completely independently from AMCAS application review and are not in any way needed for verification
6) Letters get assigned by you per school. Make sure you have read the specific letter requirements for each school you apply for minimum and maximum number and letters and who they must be from.
7) Committee letter requirements are set by the Undergraduate school and do not, repeat, do not need to adhere (mostly) to the individual letter requirements.
8) personally, I am not a fan of a professor requiring you submitting personal statement or MCAT score to them. Frankly, them repeating information weakens the letter as far as I am concerned
https://www.aamc.org/system/files?file=2019-09/lettersguidelinesbrochure.pdf