Instagram switching to PROFESSIONAL account hurts reach

Goal: More followers and likes

I have a public "personal" car page - posting photos/videos of my car. (Daily, once, same time). I have about 36.3K (all relevant followers / fans).

The performance and growth doesn't remain steady for a long time and I've done several testings. Normally I get average likes of 1,000-2,000 per post. However, during certain weeks or months they drop down to 600-700 likes. Regardless of being a personal or professional account.

I've found that a personal public profile gives a better reach/likes/follower increase than a creator/business. IS THIS TRUE???

What else could I be doing wrong? I follow a schedule such as:

• Post once, everyday (except Saturday) at: 7:40 am EST (found this to be the best time)
• I use 15-17 hashtags (I have 3 hashtag lists, so i don't repeat the same for each post)
• I post Hashtags in the comment section, right after posting the photo (right now testing # in the captions)

Reach is dropping.. thinking of switching to Creator mode again, but will that help?? btw i find the insights useless, for example, the best times to post given isn't accurate.

I'm at GMT+3, which is 7 hours ahead of EST. I changed the time in my phone to EST and the "best times to post" were EXACTLY the same ... are they using my timezone, or my most followers' timezone?