I'm curious whether you had in mind any kind of benchmarks (which have not been implemented) for checking size and/or performance differences...

For E4VM I engineered it so that my Huffman-compressed BEAM bytecode would be much smaller, at some reasonable performance cost. Something like 1:3..1:6 ratio, probably even better. The emulator code was also planned to be very limited, possibly the language will also become a subset of Erlang, to cut on the features. But there were no numbers, there was no definite goal how small I want it to be. Such talks begin when there is a project or a customer and a target to reach.

For ErlangRT the original idea was to reproduce some subset of existing Erlang/OTP emulator features and then optimize from there. It resembles Erlang/OTP data formats and data structures, so it would begin at 1:1 ratio or maybe a little worse like 1.1:1 or something because Rust incurs some costs for compound types where for C it was enough to have an integer.