Internal role regrets

Looking for general advice. I’ve been an admin assistant for four years with my current company decided to apply for a senior EA role. Got the job accepted the offer, which include included a bump in compensation. I’m technically still with my old team but started training with the new team before the senior leader’s current executive assistant retires. I interviewed for 30 minutes with executive I’ll be supporting and generally had a good feeling and while the interview was quick all of the duties were in line with what I’m already doing. Day, one of training, major, red flags. Back to back back-to-back meetings, executive accepts every invite to meetings, refusing to say no to anything, current EA must send daily updates on everything that they’ve worked on throughout the day, major micromanaging. My old role hasn’t been backfilled yet. Do I try to go back now as there is a small window of opportunity before my role is backfilled? I believe my current manager would be happy to keep me however obviously this might ruin any chances of internal movement in the future and I could also be seen as a flight risk. My fear is that if I fully commit to giving this new role a few months, my only option will then be to look external if I’m extremely unhappy. My company pays very well with excellent benefits, so my preference would be not to leave the company. Not sure what to do. I feel like I have to make a quick decision in a short amount of time. I realize I should’ve have gotten more information on the new role before accepting. lesson learned.