The usual cautions for buying on
eBay apply, plus the need to make absolutely certain the iPad will be removed from the previous user's iCloud account. It isn't always a matter ill intent. Some people don't know or understand the steps to selling an iPad. My best advice to make sure you have solid contact info for the seller, just in case.
Keep in mind that you can often get refurbished iPads from Apple. The saving isn't much, but they come with the same warranties and repair services as new iPads. And the batteries are always new, so you get the same battery longevity you'd get with an unused iPad. Low savings, but low risk.
Other than that, any model 2018 or later will easily do what you specified. I suggest getting the newest you can afford. It will save you money in the long run. Newer models will remain compatible with updates longer.
If it does not come with an Apple Pencil (gen 2), consider getting one. There is nothing better for drawing on the iPad.
I consider a decent keyboard case a necessity. I was pretty happy with the Smart Keyboard Folio on my old iPad Pro, but was seriously intrigued by the trackpad on the new Magic Keyboard for the iPad Pro so I got it with the new iPad. I'm happy enough with it, but it turned out to be a compromise rather than a pure upgrade. The folio was more flexible in the ways I could use it, and lighter. The magic keyboard is a better keyboard, but much more laptop like in it's use.
Still, the trackpad does help, mostly when I'm doing a lot of typing/keyboard work, and with the occasional app or website that doesn't work well with the touch UI.
There are lots of third party keyboards to consider as well, so don't rush into a decision.