I am about to start working remotely for a U.S. company while residing in Spain, my home country within the EU. I anticipate needing to travel to the U.S. 3-4 times a year for conferences or training sessions, with each visit lasting no more than a week.
Should I use a business-related (B-1) visitor visa or the ESTA for these trips, or is there another type of visa I should consider applying for?