I know that
Disneyland is much smaller than Disney World, so is 1 day at each park enough?
The general recommendation is at least 2 days at DL and 1 day at DCA. Of course, if you have more time, you won't be bored.
Note that, while the footprint may be smaller than WDW, there is much more packed into each park at DLR. The two parks are a two minute walk from each other. Depending on how many days you have, park hoppers will probably be worth it.
Do we need to do lightning lanes?
Yes LL are strongly recommended. They operate like the old Genie + system at WDW. No advance reservations. You can't book your first attraction until after you pass through the entrance turnstiles. LLSP (only ROTR and RSR) do not sell out. RSR has a very efficient single rider line if you are up for that.
Also any advice on hotels, getting to the parks, etc.
Where do you normally stay at WDW? What are you looking for in a hotel and what is your budget?
What rides that are at both parks can we skip or should we absolutely do them to see the differences?
BrianL's list is in the first link above. I will copy and paste it below as well. Note that we still have Tom Sawyer's Island, the Mark Twain river boat, the Columbia, and canoes.
DL Exclusive Attractions:
Indiana Jones and the Temple of the Forbidden Eye (uses same ride system as DINOSAUR at AK)
Snow White's Enchanted Wish
Pinocchio's Daring Journey
Mister Toad's Wild Ride
Casey Jr. Circus Train
Storybook Land Canal Boats
Alice in Wonderland
Sleeping Beauty Castle Walkthrough
Roger Rabbit's Car-Toon Spin
Chip & Dale's Gadget Coaster
Finding Nemo Submarine Voyage
The Matterhorn (note this uses the same ride system as Space Mountain at MK)
Space Mountain (same theme but completely different ride)
DL Similar but not exactly the same:
Enchanted Tiki Room - longer show
Jungle Cruise - No temple/tunnel, a bit shorter
Pirates of the Caribbean - longer with more show scenes
Haunted Mansion - even without the Nightmare overlay it is slightly different
The Many Adventures of Winnie the Pooh - quite simalar, though vehicles are different cosmetically - look for a CBJ easter egg!
Big Thunder Mountain - some additional effects and scenery
it's a small world - very similar though with Disney cahracter peppered in - it does have a much nicer exterior.
Autopia - much longer than the Tomorrowland Speedway, but basically the same
Buzz Lightyear Astro Blasters - removable laser blasters make it a little better (Note that this is soon coming to the WDW version)
DL Exactly (or basically) the same:
Peter Pan's Flight - technically some minor differences
Dumbo
King Aruthur Carousel
Milennium Falcon: Smugglers Run - all of Galaxy's Edge is practically identical
Rise of the Resistance
Mad Tea Party
Mickey and Minnie's Runaway Railway - The queue is very different and cool - may be new to you and is worth it if so.
Star Tours
Astro Orbitor - though at ground level
CA Exclusive Attractions:
Monsters Inc. Mike & Sully to the Rescue
Guardians of the Galaxy: Mission Breakout - based on Tower of Terror, though the DL version works a little differently
WEB Slingers
Radiator Springs Racers - this is like a massively bigger Test Track
Luigi's Rollicking Roadsters
Incredicoaster
Inside-Out Emotional Whirlwind
Silly Symphony Swings - though this is an off-the shelf "wave swinger" ride
Jumpin' Jellyfish
Golden Zephyr
Goofy's Sky School
CA Similar but not exactly the same:
Mater's Junkyard Jamboree - the same as Alien Swirling Saucers
Grizzly River Run - longer version of Kali River Rapids - definitely a wet ride!
CA Exactly (or basically) the same:
Mickey's Philharmagic! - smaller screen though
Turtle Talk with Crush
Ariel's Undersea Adventure - same as Under the Sea: Journey of the Little Mermaid
Jessie's Critter Carousel
Soarin' (Soarin over California during the Food & Wine Festival & Soarin over America starting July 2026)