Is there a printed manual on all this (expletives) new stuff?
No. However, if you have a specific question, feel free to ask on this site. Please ask a single question per post. You can ask multiple questions in a single post if they are very related, but if they are different questions, please ask in different posts.
What is a boot partition? Why doesnt it say minimum size? What is an EFI partition? Size again?
The EFI partition is necessary to boot UEFI systems, but it is not necessary if you have an older BIOS system (which were present in all computers before the Windows 8 era). 512 MB is usually good enough.
A boot partition is necessary if you want full-disc encryption. It is also necessary if your computer cannot see boot files far from the start of the disc. For such computers, a boot partition (512 MB to 1GB) would be necessary.
If you have an older BIOS system, then just having a system partition (and optionally other partitions for storing data) should be adequate. A separate swap partition is not necessary (see below), but you can also use it if you have it and want to use it.
What no swap partition?
In recent versions, Ubuntu uses a swapfile. No swap partition is necessary. But if you already have a swap partition, you can still use it. Just configure that partition to be used as a swap partition during installation.
What is snap?
Snap is a package management system, similar to APT. See Why is Ubuntu moving to Snap packages? for more details. Please be aware that snap packages are slower than their deb/apt counterparts in older computers without SSD, and also have a lot of bugs like unable to access user files.
Nowadays, Ubuntu packages Firefox and Chromium as snap (not pure APT) packages.
If you want to use firefox without snap, see How to install Firefox as a traditional deb package (without snap) in Ubuntu 22.04 or later versions?
So i usually use a 20gig
Currently, the minimum recommended system partition size is 25 GB. However, you will need at least 40-50 GB or so in the system partition to comfortably use Ubuntu, especially if you install a lot of programs.