I believe you are correct and clubs are only able to sell a maximum number of season tickets, and have to leave a certain % available for match day purchase.
6 of us booked on a coach from Coventry city centre at 12pm, all meeting at The Spongate at 9am for large breakfast and a couple of beers (fruit shoots for the 2 kids).
Yes, you should be ok if you already have a registered account on CCFC.co.uk
https://www.ccfc.co.uk/news/2023/may/tickets-next-play-off-final-sales-period-begins-10am-on-monday/