I researched many different varint encodings for a GraphQL-specific binary format (resulting in Argo: https://github.com/msolomon/argo ). I ended up choosing protobuf-style zig-zag varints, but I also found these interesting:

vu128: https://john-millikin.com/vu128-efficient-variable-length-in...

metric/imperial varint: https://dcreager.net/2021/03/a-better-varint/

vectorizing VByte: https://arxiv.org/abs/1503.07387