Actually, as you are new here, Welcome to Flightaware.
Even though I live in Canada!!!, I’ll give you the tools to answer your own question.
As aircraft landing at SNA John Wayne Orange County Airport have to clear the Santa Ana Mountains they certainly aren’t flying to low, or they would all be in serious trouble.
I would assume Ontario Airport is closer to you, and March Air Force Base with a squadron of KC-10 tankers isn’t too far away either. Corona Airport with light GA traffic, and Riverside with bizjets are also close by.
However, I’ll assume the aircraft you have referred to are airliners, and are flying in a southwesterly direction on approach to SNA.
Here is a free website, that shows the arrivals and departures in your area. You’ll be able to see the aircraft that fly right over you. Just click on each individual aircraft for the height it is flying.
It is 10 minutes behind in real time, and you can set the date and time to see replay of past flights.
John Wayne Airport
You can also listen to the approaching aircraft, and be able to track them on Flightaware. Here is the Air Traffic Control site;
LiveAtc just scroll down to KSNA - Orange County California.
You will hear the interaction between the controllers and pilots.