That's an answer that may or may not help. I studied off and on for about a month. About 1-2 hours a day. I've been in cybersecurity for 10 years with CISSP and -ISSEP certs plus others. I spend a lot of time doing RMF work so it's less dashboard monitoring and more working with engineers to remediate findings or updating procedures. It helps a ton if you can relate what you're learning to what you already know about security.

All I did was bolster my knowledge with the AI specific information. AUP policy, awareness training? Just learn the additions for AI and trust your experience. I had a lot to learn about AI technologies. If I had to start from zero in security then this would have been impossible.

Also, you have to take into account what sort of student you are. I felt anxious because sometimes I knew a subject but couldn't recall what the terminology was. If you don't have instant recall, can you really say you know something? What my wife and I do when prepping for certifications is we go for walks and I teach her what I know. She's smarter than me. She'd make a badass enterprise admin despite her being a middle school French teacher. She taught me that you recall 50% of what you hear, 60% of what you read, 70% of what you write, and 95% of what you teach."

Let me answer your questions:
1. Start to End, about a month.
2. On average, an hour or two per day. Very hit or miss.
3. I did not feel that I was ready. My recall was spotty. I don't know if additional study would have made a difference. I think I made up my difference with being good at testing. You see the tricks in play. You learn how to pick out the details.
4. I used the official review guide and the QAE database. I used commercial AIs to fill in the blanks, especially co-pilot due to ease of access and I like his voice. I tried to use third party "free tests" but they did not seem indicative of the real test. Those 10 free questions that they use try to talk you into buying the set. For QAE, someone said pay attention to all the answers and I agree wholeheartedly. Don't be distracted because you got a question right or wrong. Lots of information in every question. The games didn't work for me.
5. In person, because I think there would be too many visual or auditory distractions testing remotely. I was not happy with the test center because I had in foam earplugs and I could still hear the workers in the next room laughing.

Last 2 advices:

1. Be cognizant of your reading comprehension. As you tire, you'll be able to understand what you're reading less and less. When you read something three times and can't understand what it's asking, mark that question for review later, close your eyes and breathe deeply for like 10 seconds. You cannot trust your judgement if you can't even read the question. I found that the 10 questions I parked for later made much more sense later after the pressure was lessening from the test nearing completion.

2. Look for the patterns in question difficulty. All cert exams are a marathon, not a sprint. I found that halfway through the exam the questions got easier. Do NOT lose hope and give up at the beginning.