Of course it depends on what software you are using.

Though as a rule of thumb, peers try to connect directly. That's not always possible due to firewalls/NATs, so often TURN servers are used as intermediary.

Regarding /boot, it can be encrypted as long as your bootloader can decrypt it, for example GRUB can decrypt LUKS encrypted partitions (albeit somewhat slowly). And the only partition that really has to be unencrypted is UEFI system partition (ESP), where bootloaders are located.

While snapshots are not backups, they are very helpful when making backup because they are atomic and can also be transferred to another drive with btrfs send/receive.

Indeed, it's a bit more complex setup, you won't be able to boot without initramfs. But in certain cases (e.g. encryption or partitions spanning multiple devices) it is very useful.

It really depends on your requirements...

But a few useful points:

1. Use GPT partition table and not MBR. Everything will be simpler, no need for extended/logical partitions.
2. If you need to be able to do online (mounted) partition resizing, pick btrfs. Ext4 can only grow them online but not shrink.
3. Make sure your partition boundaries are 1 MiB aligned.
4. If you need more advanced setups, consider using LVM.