I believe the issue is only with Tailscale Funnels. With Funnels, the data runs through TS’s infrastructure so it’s subject to whatever kind of bandwidth limitation they feel like enacting.

As others have said, you don’t need to know how to code, but you do need to be comfortable editing structured documents, so knowing a little programming does help.
Unfortunately, Nextcloud and email are two of the most difficult things to self-host. This is by reputation, I haven’t tried myself. Email is supposed to be particularly difficult and the usual advice is to not bother.
Jellyfin is pretty straight-forward as long as you don’t have a weird hardware decoding setup and as long as you don’t want remote access. If you do want remote access you need to use third party tools to do it securely. If it’s just for your own use then Tailscale makes it really easy. If you want to share with non-technical users it gets messy.

I went with Debian and I use Docker for containers. I considered Proxmox, but I didn’t end up trying it. PiHole is a good application for the Pi Zero (I have an early generation Pi dedicated to running PiHole), but you could also run it on the Beelink.

I strongly recommend you download Obsidian and keep hyperlinked notes on everything you do and links to every tutorial/resource you end up using.
Have a place to keep all the passwords your services will end up needing. A password manager is the best option. Make the password on your admin account on Debian (or whatever) easy to remember and enter, since you’ll need to sudo a lot.
If the Beelink comes with a copy of Windows installed, you can recover the key from within Linux with the following command:
sudo strings /sys/firmware/acpi/tables/MSDM
Then you have a spare Windows key should you ever need one.