Another vote for being professional. Your previous employer may be a turd but that doesn’t mean you should be one.
If there is no chance that they will listen to anything that you have to say, just tender a polite, professional resignation. Do not say one bad thing.
If you think that somebody might actually take some of your advice, present it in a constructive fashion, the way you would want to hear it if you were on the receiving end.
Either way go out as an adult.
There are a couple of reasons for doing it this way. One, frankly, is that you are an adult so you should act appropriately (we’re talking about your professional life here, not what you do in your spare time with your friends).
Two, you never know the next time you’ll meet some of those people again in your working career - maybe the old boss will get hired as the new boss at your new job and if he remembers you as the guy who called him a poo-sniffing goat felcher that may negatively impact your future.
Three, even if you don’t work with them directly again you may move in the same circles. Rightly or wrongly people talk, and you don’t want someone saying “Oh yeah, Blucher was the guy who took a crap in my mailbox the day he left.”
Years ago I worked at a major public utility. A guy left the support center for a better computer job elsewhere and decided that since he was gone he could express his pent-up animosity towards a former coworker (and her mom, also employed at the same public utility). Unfortunately the PU was the largest customer of the fellow’s new employer. Two managers called his new job and got him in horrific trouble - “Hi, I’m a manager at XYZ Corp, your major customer. One of your new employees is harassing several of our folks…” The guy was dragged into his (new) boss’s office, had to explain his behavior and apologize in front of everyone, he was crying, realized he might get canned from his nice new job in the first week, etc.
So celebrate, get tipsy, have a great roll in the hay, fantasize about all the stuff you’d really like to say to your old boss and just leave it as safe venting outside of the work environment. There is really no advantage to getting “revenge” when you leave, it won’t do any good and it may bite you in the butt later.