First of all, congratulations! How exciting! And I think a honeymoon at Disneyland will be delightful. My husband and I have gone several times to celebrate anniversaries.
1. When are you able to start booking resorts/purchasing park tickets? Is there a general idea as to when May/June will come available?
If I remember correctly, Disneyland hotels will allow you to start booking for the next year sometime around August or September. I believe that in the past the entire year opened up for availability at the same time, so I would start checking periodically this summer, but definitely start looking in August or September. Unless you are looking for a hard-to-get suite, you should have pretty wide open availability if you book in fall of 2022 for a stay in the spring/summer of 2023. The spring discounts for 2022 just came out a couple of weeks ago, so if you book a room this fall or winter, make sure you keep your eyes open for discounts in February or March 2022 to see if you can get a discount. I recommend purchasing your tickets and making your hotel reservation separately instead of doing a package because it's much easier to make changes when you book them separately.
2. What is your favorite resort to stay at here and why???
My favorite resort hotel is the Grand Californian Hotel. It's gorgeous, comfortable, and I love it's proximity to the parks. I love the views from the rooms. My favorite view is of Downtown Disney and while some complain that those rooms get too much noise coming from DTD, the noise has never bothered my family and my husband and I love to sit on the balcony sipping a glass of wine and people watching. The Disneyland Hotel is also fun and very nostalgic but there is a lot of construction going on right now and I don't know if it will be far enough along a year from now to not be an eye or ear sore. It's also a further walk all the way at the other end of DTD (though you can take the Monorail almost all the way there from Tomorrowland). I do not recommend Paradise Pier. It's okay, but not worth the price. I would rather stay at my favorite off-resort motel (Park Vue Inn) that's right across the street before spending the money to stay at Paradise Pier.
3. Best dining and why??? Napa Rose is hands down the best dining at DLR. It's the flagship restaurant at GCH and the food is incredible. Many people like doing the chef's counter and my husband and I have done this and enjoyed it, but we actually tend to prefer dining at a table. The wait staff at Napa Rose are just fantastic. Blue Bayou is my sit-down restaurant at Disneyland (it's located inside Pirates of the Caribbean and the ambiance is very romantic) with Cafe Orleans being my second favorite. Carthay Circle is the "nicest" restaurant at DCA, but I've really found the food their to be hit and miss.
4. Three park days and one resort day--does this sound good/doable? I know it's smaller but having never been definitely want some time to stop and smell the roses. We'll probably be doing West Coast National Parks afterward.
Hmmm...you'll get different answers here. If it were me, I would probably buy four day park hoppers and use the extra day to be able to take my time exploring the parks without feeling rushed and to give myself time to go back and do favorite rides or activities. Especially since you want to stop and smell the roses. My family is going for four days with three hotel nights/three park days on our next trip. We plan on stopping to smell the roses, spend some time at the hotel pool, some time at the Tenaya Spa, having a few nice meals and by doing this we are well aware we are definitely NOT going to be able to make every ride or do every activity. And we are okay with this because we tend to go once a year or so and know we will be back. Unless you are planning on spending a good portion of a day at a pool or going to the spa, a whole day at one of Disneyland's resorts might be a little long.
5. Anything honeymoon-specific worth doing? Let the hotel know that it's your honeymoon when you book your room (or call afterwards and let them know). My husband and I entered our room on an anniversary trip to a bed decorated with rose petals in the shape of a heart. Ah, Disney magic!!!! Get Celebration button (I'm not sure if there are specific "Just Married" buttons, but if they are, make sure to ask for them! Splurge on those little extras. Maybe take an afternoon break at the Tenaya Spa to treat yourselves to a foot massage on your 2nd or 3rd day of the trip. Or rent a cabana at the hotel pool for an afternoon. Reserve seats for the dessert party at World of Color or plan a Blue Bayou dining package for Fantasmic! Have dinner at Napa Rose. If eating at a sit-down dinner in one of the parks, order one of the special cakes prior to your trip to be delivered to your table as a surprise. Make a wish at Snow White's wishing well. Get a silhouette made of the two of you on Main Street. Enjoy some happy hour drinks at Trader Sam's at the Disneyland Hotel.
6. Does Disneyland use a system like Genie+? Worth using, or no?
Yes, Disneyland uses Genie+. It wasn't in place on my last trip last summer, but I do plan to use it myself on my upcoming June trip. It's a little different than WDW's version from what I understand with many more ride choices and not limited to 2-3 rides. But I don't have first hand experience on whether it's worth it or not yet, so I'll let others chime in there. But my 2 cents is that it's not that much more after spending so much money on the rest of the trip and I see it as "insurance" to help minimize my time in lines.
7. Miscellaneous! Anything else worth knowing on the front end? Yes, buy park hoppers! Disneyland and DCA are literally right across from each other. When you walk out of the gates of one park, it takes just a minute to cross over to the other park. Don't forget to make your park reservations when you are about 120 days before your trip (though they don't book up until about 3-4 weeks before hand and the resort hotels do have a special bucket for reservations if needed). Dining reservations at Disneyland open up 60 days beforehand (usually, sometimes 59, 58, or fewer days) and you have to make them day by day unlike WDW where your booking window opens up for your entire trip.