How much money do you keep in your checking account?

What amount do you consider comfortable?

If it’s less than $2,000, I worry that my mortgage payment will bounce, but if it’s more than $3,000, I worry that I’m missing out on interest.

Is there an easy way for me to keep my money in a high-interest savings account until just before I need to make a mortgage payment? I would want it to be an automated transfer, so that I could never forget.

I’ve looked into interest-bearing checking accounts but the interest rate is typically so low it’s not worth it.