Since swapfile shouldn’t be in a snapshot, and I want my system encrypted therefore I am asking if it could be possible to make efi partition big enough to include swapfile inside it?
I can’t find documentation for this process, so would it require some extra steps to make it work?
Just follow the instructions here. Snapshots do not recursively traverse subvolumes. So putting the swapfile into its own subvolume means it will be excluded from any snapshots of / . The command should also set No_COW which also implicitly turns of compression if you use that.
I’ll repeat what another user said because it’s important. If you want filesystem encryption you also want swap encryption. Otherwise any data is liable to get leaked by being written to swap.