Actually, your email delivery will depend on multiple factors.
The main factor is your sending IPs/domain reputation which only builds if you are using a good email database (without any bounce and spam traps).
Your customer action will also matter such as if they engage with your email (open click and reply), similarly, if they mark you as spam then it will count also but as a negative signal.
We usually calculate the email deliver based on the open rate, how many people actually read your email, and that could vary from sender to sender.
Check our article on Inbox delivery.
Gmail will further classify your email as Pomortional based on your email content (mostly bulk emails).
Email such as one to one email and or else you are already present in your customer's contact list or you communicated in the past with the customer can help your email to place in the Inbox.
Gmail considers the personal behavior of users too such as their likes, dislikes, hence it could be possible that few emails go to promotional, and few into inbox or few in the spam or junk folder too, depending on how that user behavior with the other similar emails.
Although by changing your email template you can increase the chances of landing email from promotional to Inbox folder.
After the setup, our team will share the tips and tricks and get better delivery, so you can follow that in order to perform better and get better email inbox delivery.