There are currently two tiers in my Ko-Fi membership: the $1/month tier gets early access to the monthly freebie plus a 20% discount on all digitial purchases through the Ko-Fi shop, the $5 tier gets that plus at least one free design a month, and the $15 tier gets all that plus one advanced design. Regular designs remain free for three months, so when you join at the $5 level you get access to at least six designs (of which two of the smaller ones are free to everyone). Advanced designs are a one-month-only deal.
Regular designs always have at least one option compatible with 4x4 hoops (the Blue Shark, for instance, had two sizes that fit in the 4x4 hoop, and four more for larger hoops). Advanced designs sometimes make this impossible, but I'll warn you in advance if that's going to happen and you can skip or reduce your subscription that month.
The advanced-design tier isn't available yet - it should launch in April, but the impending move may result in that getting pushed to May.
Freebies drop by the second Friday of the month, advanced designs drop by the third Friday, and regular designs drop by the fourth Friday.
Ko-Fi doesn't automatically put these in your account, it only gives you access to them. Be sure to download them when you have access! (But if you miss it the window don't panic, just let me know and I'll catch you up.)