This is all just my personal opinion. This is my advice to section hikers who want it.
These recommendations are roughly in order, but I did not number them because the order really depends on how logistically complex someone is willing to get, how far they want to hike, and how much elevation change they want to deal with.
All of Section J
This is one of the beautiful sections and by far the easiest logistically. You can take a bus to/from Stevens Pass and getting a ride to/from Snoqualmie Pass is easy because so many people pass thru there.Also, it has many exit points in case you need to get off trail for any reason. It has two challenging stream crossing in the spring (Lemah Creek and No-Name Creek above Hyas Lake). I recommend Starting at Stevens Pass only because hitching a ride from Snoqualmie Pass is so easy. Or, if you can manage the logistics, I like to go northbound and add part of section I to the trip, Stampede Pass to Snoqualmie Pass.
All of Section L
Perhaps the most beautiful section of all, but has logistical challenges. Because we cannot cross into Canada, we must hike to the border, turn around, and hike back out. That's a minimum back-track of 30 miles to Harts Pass. This section might be the easiest in terms of elevation change (especially between Grasshopper Pass and Hopkins Lake) because it keeps you pretty consistently between 6,000 and 7,000 ft. This section is the furthest east of the Cascade Crest and is the most prone to wildfires and smoke issues so that is a reason to try to get it done early in the season. Another reason for a spring hike is that water availability is not great in this section. There are no challenging stream crossings in this section.
Part of Section H, Goat Rocks
The north part of Section H is in the top four two most beautiful sections. At the south end it can be accessed at Potato Hill, Midway, or from Wallupt Lake. All entry points require a long drive on a dirt road. The north end is White Pass, a paved highway with a store and a hotel. This section includes Old Snowy, the highest point on the PCT in Washington (low route) and the highest point in both WA and OR (high route). In fact, the high route is the highest point in the northern 1,121 miles of the PCT. The PCT won't reach that same elevation again until 745 miles south at mm 1535. The high route melts out rather early, but the low route melts only by early October. I avoid this section until I know the high route is clear. The low route is a simple traverse but has a long run-out so anyone who slips without an axe will slide a long distance. Goat Rocks also includes Knifes Edge which is exactly what it sounds like. It's really no more dangerous than any other steep slope on the PCT, but feels otherwise because there are slopes on both sides of the trail. There are no challenging stream crossings in this section.
Part of Section I, Chinook Pass to Naches Pass
Middle third of Section I. This portion of the trail is fairly high and offers amazing long distance views of the surrounding volcanos. It's high, exposed, and is where water is the most scarce. There is plenty of water at both ends (Sheep Lake and Naches River) but has only two other sources between and both require a little off-trail searching. This section ends at the Mike Ulrich Cabin. There are no challenging stream crossings in this section.
Part of Section K, Sauk River to Stehekin
Normally I'd call this Stevens Pass to the Suiattle River, but the Suiattle River won't be a valid exit/entry point for some time now. So starting in 2026 I'd recommend entry vis the Suiattle River and exit at Stehekin.
This is the part of the PCT that wraps around Glacier Peak. This is arguably the most beautiful section but is by far the most difficult to hike and has logistical challenges. This section also recieves the least trail maintenance and has many blow downs and washouts. The Kennedy Creek crossing is possibly the most dangerous in the state because of the size of the watershed that feeds it. More solitude is a big advantage to this section. Once you are in, you are committed to some miles, especially in 2026 with very limited access points. A huge pro for this section is the beauty of Glacier Peak. This section requires an investment in planning and effort, but that investment will pay off big in beauty and satisfaction. There's a very cool alternate route and a side trail at Suiattle Pass. You can even add Spider Gap or Buck Creek Pass if you want to get fancy.
Part of Section H, Williams Mine (Trout Lake) to Midway
(or just continue on thru Goat Rocks to White Pass) This section involves climbing up Mt Adams to about 6,000 ft, then circling its western slope, then hiking past the northern lava flow to a cinder cone (potato hill).
Part of Section I, White Pass to Chinook Pass
This section has two distinct halves; from White Pass to Fish Lake there is effectively no elevation gain after the first four miles, the forest is more open, and there are many lakes and ponds. North of Fish Lake you climb up to the Cascade ridgeline and its a ridge hike the rest of the way, with limited water until you get to Dewey Lakes. Then you climb again up to Naches Peak and Chinook Pass. There is only one easy creek crossing at the Fish Lake outlet. For consistency I just described the trail south to north, but this section has a clear elevation advantage going southbound instead.
What to skip
Okay, don't get mad at me, this is just my opinion, but here's the sections I would skip if I had limited time to hike:
Section H - Columbia River to Williams Mine. (There is a fair argument to be made for Indian Heaven, its just lower in my personal ranking)
Section I - Naches Pass to Yakima Pass.
Section K - Suiattle River to High Bridge.
Section K - High Bridge to Rainy Pass