exFAT is an extension of the FAT32 filesystem that allows for larger drive sizes and file sizes and is mostly used on SD cards. Despite the name similarities it has nothing to do with the ext filesystem, and won’t support the same features as it (such as symlinks).

1000 mbps is the theoretical limit of the line. You will typically lose a little bit for things like TCP overhead.

Link bandwidth (Mbit/s): 1000
Max achievable TCP throughput limited by TCP overhead (Mbit/s): 949.2848

There is a snap package which should be more up-to-date, but I’m not sure I would recommend that for an editor. Compiling from source would be fine, as it will default install into /usr/local and shouldn’t affect the existing install. Afterwards you may need to update the link to emacs in your /bin folder (manually or via update alternatives) or add the folder where the new emacs is to your path at the front.

Dunno what rock you were hiding under but this is absolutely possible in a hosted environment. There’s even ESXi documentation on how to do it. Taking a snapshot can be detected, but can’t be prevented. These memory dumps can include encryption keys, private keys (such as SSL certificates) and other sensitive data.

Unless you can physically touch the drive with your data on it, I would not store any sensitive data on it, encrypted or not.