Where are you staying? Are you staying at the same place for the entire trip? And how many do you have? That is the key.
DLR, Knotts, and Orange County beaches are about an hour away from the Hollywood area where Universal/WB Tour is located, and also an hour away from Santa Monia Pier which itself is 30+ min away from the Hollywood area.
In 2019 my fiancé and I (2 people) did a Southern CA trip seeing all of these sights using only Ubers/hired cars for the first 5 days, then rented a car for the last 2. Honestly, having the car sucked for us. The Ubers were SO great to not have to worry about directions, traffic, parking, drinking, you name it. However, the key was we stayed in 3 different areas, and we only had 2 people so we only needed regular cars. Here is a breakdown of our trip:
1. West Hollywood - stayed at the Farmer's Daughter hotel. I HIGHLY RECCOMEND THIS HOTEL!!! It is across the street from The Grove which is a large outdoor shopping and dining area. It was fabulous. We Ubered there from LAX, then while we stayed there we did Universal, a Hollywood tour where they drive you around in an open air van to see the sights, and hit up some various museums and famous food places. We only used Uber/walking and it was great.
2.
Disneyland - we stayed at Desert Inn & Suites across from the resort pedestrian entrance. Wouldn't necessary recommend the hotel, but wouldn't dissuade you from staying there either. Let's just say the location is what made it acceptable. To get from West Hollywood to Anaheim, we hired a car through Limos.com. I did this because I knew it would be an hours drive in heavy traffic and I did not want to deal with the possibility of a bad Uber driver. We got picked up in a luxury SUV and it was great. Once we got to the Disneyland area we only walked to and from the parks, never used Uber. For you though, you'd easily be able to Uber to Knott's from your DL area hotel.
3. Santa Monica - we rented an Airbnb and a car, picked up the car from the Disneyland area, and made the hour drive up to Santa Monica. The Airbnb was in a not great neighborhood, and I hated the stress of driving the car. We did use the car to drive out to Malibu along the Pacific Coast Highway which was cool, but that still wasn't worth the hassle of it all, and we could have done a Malibu tour or something to see it instead. I wish we had spent the extra $$ for a resort along the main drag/beach by the pier and relied on Uber again. We went to a taping of Wheel of Fortune and did other touristy things in that area. We ended in that area so we could be close to LAX for our flight home.
All in all, it was totally do-able only Ubering and I wish we didn't rent a car at all. HOWEVER, we could only make that work because we stayed in 3 different areas and made the hour drive between Hollywood, Anaheim, and Santa Monica on 2 of our days. Now, did we save money Ubering? Probably not with all the fares and tipping. However, we also never needed to pay for parking and we had a few nights where we went out drinking and never had to worry so it was money well spent for us.
The best thing we did when staying in West Hollywood to see a lot of sights in one go was taking one of the "tourist traps" tours. We did a short one that was 3-4 hours long and only stayed in the Hollywood/Beverly Hills area. However, they have full day ones that take you to Malibu and the Santa Monica Pier as well. Looking back one of those longer options would have been better for us to see everything with less hassle. I know some people might find those tours lame or a cash grab, but to us to showed us everything we needed to see. I mean, we are tourists after all!
I hope this helped! We had such a fabulous trip and would do it all again in a heartbeat.