All kids get antsy, especially our kiddos. What has worked for us is allowing our Daughter to stand while doing homework, she would wander away, which we allowed as long as she came back to work on her schooling. She eventually grew out of the need to stand and could sit for longer and longer periods of time. No medications needed.
With our Son, we had a big exercise ball for him to roll on, sit and bounce with his bottom on, and smack with his hands on. He was also allowed to roam as long as he came back and tried.
Meltdowns can be greatly reduced when you discover what is causing them. Usually, it's a combination of things. *Our kids don't like to have sudden changes in their schedule, so letting them know ahead of time and reminding them a few times beforehand helps. ( You can even set a timer, and point to it.) *Sensory issues, such as bright lights in stores, sounds hurting their ears, clothes they don't like the feel of, can all trigger a meltdown. Gunrange earmuffs work great for hearing sensitivities, so do special earplugs for people with sensory issues. Wearing sunglasses can help shield them from light. Smells can be triggering as well, with us we had to stop going into certain craft stores that had scented pinecones, etc... To help with not liking to wear things they need to wear, (such as shoes, gloves, hats...) try desensitizing the specific area by gently but firmly pressing, or squeezing the area before putting the clothing on. (This also works for toothbrushing... press/rub cheeks, lips, outside of mouth, and allow kiddo to chew something chewie T or gum, right before brushing.
*If a child is having a hard time with meltdowns, it can also mean they aren't feeling good. Toothache, headache, stomachache, etc...
*Difficulty communicating can be a big factor in meltdown. Using a tablet with an app to talk, or using pictures to point to, or PEC cards which can be found and printed off of the internet for free work great. I also recommend reading the book "More Than Words," by Fern Sussman. To help your kiddo learn to communicate. It's very well written and easy to understand what she's saying. Also "Baby Bumble Bee" and "Signing Time" Makes great videos for the kiddos to watch and learn new words and helps with communicating.
I hope some of this has helped. <3 You've got this! :) Things will get better.

Too early. Brain is still developing, and you need meds as last resort.

I can see why you're uneasy about giving a 4-year-old medications. I guess it would depend on what kind the doctor wants to prescribe. A lot of these medications can wait until the child is older to see if they really need them or not.

I felt exactly the same way after my son's diagnosis. The support system is so broken — we were given a pamphlet and sent on our way. That's actually why I created Nova, a real-time support tool for autism parents. Because no parent should have to figure this out alone in the middle of a meltdown.

Sorry but I'm not the it's okay for Jane to med her kid so it's ok for mine too. This is really one of the hardest questions you'll ask yourself as it's not the if this goes well it's typically what happens if this goes wrong. You'll have just as many people who didn't med their kids as there will be who did and still do. No one and that includes our kiddos PEDs know what will happen to your child on whatever meds. They said the Covid vaccines were safe then people who family died reminded them that it's not necessarily a fact. Young kids still developing given drugs just isn't my cup of tea but that's just me. At this moment my Lela age 11 is more tantrum full on destruction mode then a meltdown. She's had about five meltdowns this year I stopped counting tantrums as those are too regular. I remember a parent asking about discipline and I couldn't stop lmao like learn your kid please. That wasn't an insult that was insight! We the Parent have to learn our children and yea it's pretty damn hard but that what makes it worth it. I always look at my Lela as a big puzzle of WHY did she do this instead of that, now I add that with her other tendencies and put all that together every day to keep her on track. No one has all the answers, but we can should and will continually share what's worked and what hasn't and hope for the best in between while we figure out the rest.