I have used the private car hire, the taxi at the airports where you get a number to a taxi station, Grab, Bolt as well as the Airport Railink connecting with BTS Skytrain.

While the private car hire and airport taxis were most convenient, I soon relied heavily on Grab for all my rides to/from the aiport and sometimes around the city. I liked the drivers, as they are pretty friendly and honest. On this most recent trip, I started using Bolt more because they were offering 10 to 15 % discounts. I must say that I have been quite pleasantly surprised with the quality of cars, the promptness of pickups, and most importantly, the price.

I know someone alluded to previously that someone could save less than $15 dollars if you think in terms of US dollars. However, I didn't pay thousands of dollars for my airfare ticket and fly over 20 hours each way to a foreign country to think of pricing as in terms of US dollars. I think in terms of baht. But, hey, that's just me.

For the previous poster who asked about the different options, I strongly encourage either Grab or Bolt as they have been pretty reliable, and during your time of arrival, there should hardly be any wait. My most recent airport pickup was 227 baht from the airport, with 25 baht toll. The private car hire is 900 baht, so a difference of over 600 baht, which is almost $17 US difference, which you could direct some to a nicer tip to the rideshare driver or to another trip expense.

Now, I have taken the aiport rail link on at least 3 occasions. I have taken them when I stayed right at the intersection of terminal 21, where many times, it takes about 30 minutes for the car just to move 300 meters. While I will certainly use it again, I will only do it when I travel lightly and stay in heavily congested part of Bangkok. I still prefer the convenience of being picked up and driven to the airport in a car, be it a taxi, Bolt/Grab car, or private hire.

Anyhow, this is just more options for you to think about.

Best wishes on your trip and have fun.