I am share what I am currently doing in my class. For context, primary school teacher (elementary), currently teaching Maths, but also did English in the past.
I have been using the 2018 11" iPad Pro (though I recently upgraded to the M4 iPad Pro), which I imagine would be comparable to your 10th gen iPad in terms of performance. It's not slow, but the 4gb ram definitely shows its age.
For model, either M2 or M4 should do fine. As for size, I initially went for the 12.9" model, but returned it a few days later because I found it too cumbersome to be bringing around with me, or holding in one hand while roving around the classroom. Assuming Apple maintains their 2-week return policy in your country, you could try one to get a feel, but I would personally recommend the 11" for the improved portability.
If wifi coverage is spotty, I recommend getting the cellular version, though it will require paying for an additional data plan out of your own pocket. When my school started out, our network coverage was also pretty weak, and our school network did not play well with apps either (for example, mail was heavily filtered if yours wasn't an enterprise device), and airplay mirroring via the Apple TV was flat out disabled (necessitating that I invest in my own router until peer-to-peer airplay was a thing). Oh the days of iCloud syncing causing me to bust my meagre monthly data caps.
App-wise, I use mainly Notability. The thing about the Apple TV is that it projects my iPad in a 4:3 aspect ratio, and there's this annoying border around the screen. Notability has a presentation feature which allows pdfs to fill up the entire screen, making it both bigger for my students to see, and giving me more room to work with. It just looks nicer overall. The downside is that they recently moved to a subscription model. Not expensive, but something to keep in mind.
I have no experience with Goodnotes, though I understand they are close contenders with each other, so you should be fine. Likewise for lesson prep, I also prepare my slides / teaching material on either my school laptop or my own MBA, all of which are saved in OneDrive (I also pay for an annual Office subscription). I chose OneDrive as it is integrated with office and outlook, and it's also way cheaper than Dropbox now. If there are videos to be played, I download them (there are apps on my Mac to download YouTube videos) and embed them directly, since YouTube doesn't play well with the Apple TV.
For apps, it's a bit of everything.
1) Scanner Pro - for scanning documents
2) Camera - when I want to take snapshots of students' work, and it doubles as a visualiser when mounted on a stand.
3) Google Classroom (sucks compared to the desktop version, but I can still post stuff online).
4) Lumafusion - during the pandemic, I used screen recording to record screencasts (mostly myself annotating on pdf documents while explaining a concept), then edited them in lumafusion. I like that said app lets you upload the video directly to YouTube, saving me a couple of steps.
5) Lookup - it's a dictionary app that I like because of its "word a day" widget. I bought it when it was dirt-cheap, and if it's your thing, said feature can be a nice intro to the start of your lesson.
6) Chrome - I tend to maintain similar apps so I can draw the line between work and personal. For example, I use chrome to show websites to my students so it doesn't see my personal Safari browsing history.
7) For listening comprehension and videos, I use a document container app like Documents (this was way before the files app was available). I just prefer using multiple apps each for a single specialised purpose.
8) VLC handles avi files, though the UI is awkward.
9) Educational like Quizizz, Pcalc, Padlet, Google Drive, even clock for setting timers.
Oh, and if you are using your iPad for personal stuff as well, I recommend setting a focus mode which you can enable when entering class. This will block out annoying notifications, as well as hide your own personal apps / widgets by replacing them with a default home screen that shows only the apps you will use for teaching. For example, I have no desire to let my students see whom I follow through my Twitch widget, or my podcast or music tastes, or what games I am playing, or even my calendar events.
You may also want to disable Siri. I have had it misfire a couple of times during lessons.
In terms of learning experience, I will say it's really about being freed up to move around the room and being able to better monitor your students. It's very easy to overlook the students seated at the back and with this, you can ensure that your attention is better distributed amongst your students.
Hope this helps.