First off, you really don't want to know first hand how rough of a trip too much can be - ABV or green or mixed. Imagine being so stoned that it feels like a bad flu bug (tho without the puke and liquid shits).
Fortunately I haven't taken so much as to be nearly catatonic, but I have seen it. Not pretty! I have had a bit too much and it can be pretty rough.
Usually I make butter or oil and cook with it. This helps with dosing because all of that batch will be same potency. I usually put about 1/2 teaspoon on a toasted bagel for a test run. Eat that, and try to gauge the strength. Then I use the results to figure how much to put in cookies, brownies, on pasta, whatever.
Be careful with your low tolerance friends! I try to make my cookies so that 2 are a good buzz, 3 is a serious stoning for 5 - 6 hours and 4 of them is blotto. But, this is for me and stoner friends. Have had friends who smoke/vape about once a month and 1/2 cookie will take them to the same place it takes me 3 to get to. A person's size/weight and metabolism plays a role, too.
I gave a friend a brownie who used to smoke but hadn't for about a year. I was eating 4 (2 then 1 after 1 hour and another after 2nd hour) of the same size for a good happy all day out and about buzz (hiking/fishing/movies/whatever - stoned but pretty much able to function for 6 - 8 hours). He decided not to eat it and gave to his wife a couple weeks later. She and 2 of her friends split it. They're all pretty healthy (120 to 140 pounds), and haven't used any weed at all in years. The 3 of them were so ripped they were ready to go to the hospital because they thought they were ODing. Thankfully, they had the good sense to call me instead of an ambulance. Took me a while to get them all chilled out, but they survived fine. They also have all sworn off any weed for the rest of their lives (and any of my baked goods, spiked or not)! But, consider the math here. I do have tolerance, but not really that much compared to many here on FC. They each had about 1/12th of what I'd use for a good full day buzz and were sure they needed medical attention. So sure they were ready to "turn themselves in", no matter what the consequences.
Too much will usually put you to sleep.... eventually it will in my experience. But, the hour or 2 before sleep can be nasty. Your stomach will do flip flops, a weird edginess can come on and not leave, headaches, etc - and the paranoia can be crazy strong. It is not the same as smoking or vaping too much in one sitting. That can be rough too, but nothing like too much to eat. And the worst part is, that unlike vaping/smoking if you get too much you can't just stop and try to chill out. Once you ingest it, you're going to be on that road for a while with no offramp unless you can sleep, and no guarantees you'll sleep all the way through it.
Start small and be careful. Give it at least an hour to kick in, sometimes 1 1/2 hours to get to full tilt. You can always add a little more to top off.