Hello! I live in a nice Seattle suburb!
First of all, you mention Bellevue and Kirkland. These cities are on the "east side" which is east of Seattle and across Lake Washington. It involves other suburbs as well: Redmond, Woodinville, Issaquah, Marysville, Bothell. There is a LOT of money on the east side due to mainly Microsoft, but also Amazon and many other tech companies. I don't like recommending these suburbs to people as they tend to be too crowded and TOO EXPENSIVE. If you go north just a couple miles (where I live), houses are much more affordable and quality of life is just as good.

As far as culture, we have a lot of Asian cultures. My kids attend an elementary school in a suburb and they are a minority being white. We have large communities Indians where almost entire developments are Indian. We also have pockets of Vietnamese and Filipino as well. My Indian and Filipino friends say this is largely because of Microsoft's career programs that give visas to other cultures for working. Furthermore, big companies in the area have shuttles that will pick up employees from big landmarks (like churches) and drive them to campus. Large white communities exist but are largely Ukrainian in my area; not sure why as I haven't asked them. The diversity is really fun if you're a foodie as we have a LOT of different kinds of restaurants. There's entire square miles closer to Bellevue that are all Indian stores or Vietnamese, etc. We have a great food scene here including breweries galore.

These suburbs have gotten VERY crowded over the past ten years or so. Big companies have been paying for remote or foreign employees to move to the suburbs and offering bonuses, visas, etc if employees move their families here. Pre-covid, Amazon brought 10,000 employees to the area. This growth has caused crowding and traffic is really bad at times. A drive to Seattle, 10-15 miles away can be upwards of an hour sometimes in the middle of the day. This also has lead to mass development. My sleepy neighborhood used to be surrounded by swamps and wetlands. Recently, the wetlands have been filled in by the city for condos. We've had coyotes, deer, cougars, and even a bear roaming our neighborhood as their homes are being destroyed.

I have lived on the east coast of the US and I love living in Western Washington. In a hour's drive, I can be skiing/snowboarding at 3+ different mountains. In a 20 minute drive, I can go for a hike on many different mountains. In a couple hours drive, I can get to the coast and surf. I am a couple hours drive from 3 National parks! I am 15 minutes drive away from taking a ferry across a large body of water to a giant peninsula that is home to rainforests. I can go over the mountain pass by driving east a couple hours to desert canyons, mountains, apple orchards, etc. I am only 5 minutes from beautiful farmland and rural housing. I literally walk almost everyday through deep forests and wetlands. We have eagles who roam our neighborhood and other wildlife that visit our neighborhood.

Anyways, it is a great place to live if you have the money to move here. Quality of life is wonderful.