If you do not provide Border Patrol with access to whatever they want, you do not get to enter the country. You have zero rights at a US port of entry.
The best solution is what many US companies do for employees traveling to China -- a burner laptop & phone with no data on it.
Provide some form of remote access to services, such as webmail.
A two second google search will give you the answers you seek about what the CBP can do - https://www.cbp.gov/travel/cbp-search-authority/border-searc...
This is the answer - burner laptop and phone you can lose without repercussions.
From my extensive research reading spy novels this would be something they do entering a high risk environment. If you absolutely have to have the data onsite at client meetings and don't want to use the cloud, then separate the data from the laptop. Maybe go old school with a USB stick. Make the USB stick look like a charger. Or pack a bag of 100 USB sticks with your company logo on them as chatchkes but one of them has the data.
I have to imagine if they are going to seize a laptop they probably aren't going to let you in anyhow.