27 drops really is too much, unless you have special dietary needs. The post offices on the PCT often have limited hours (i.e. one or two hours on Saturday, closing at 4:00, etc.) and having a lot of maildrops means often racing to meet the post office schedule.
On the PCTA page there is a link to how to do the PCT without any maildrops (e.g. nearby towns you can hitch to where you can shop, if necessary) or you can buy in the larger towns, while you are on the trail, and ship to the small resorts along the way - we did that in Ashland for all of Oregon and Cascade Locks for most of Washington.
If you’ve never done a long hike, you probably won’t know in advance which foods will utterly disgust you after a month or so and which you’ll learn to like along the way. Some folks can eat oatmeal for six months - others don’t last two weeks with it. We found that we needed much larger amounts as time went on - so a box of cereal that was supposed to serve 12 would only last the two of us 3 days, at best. I soon discovered that poptarts, while tasty, didn’t keep me satisfied for more than an hour or two. Other hikers have a poptart for breakfast and are good until noon. So, by not shopping for the whole trip now, you avoid buying food you won’t eat and not having the food you do want to eat.
Ginny