The level of Cloaks/Veils outputs corresponds to the level used in the modular world. This is a much higher level than that used by the almost majority of external/usual audio equipment (level called 'line') and this is why we use an output module that will adjust to the line level required (by most mixers or recorders, for example).
Please note, the StMix is a small (but excellent) mixing module. It allows you to mix signals inside your modular and it is not designed to be an output module.
Vca: Cloaks/Veils plus Happy Nerding 3x VCA will be sufficient.
Utilities: one often recommend a matrix mixer (like this one: https://www.modulargrid.net/e/ai-synthesis-ai008-eurorack-matrix-mixer)
For more informations :
https://learningmodular.com/glossary/10-db/
https://learningmodular.com/glossary/mixer/
https://learningmodular.com/choosing-utility-mixers-for-your-modular/
PS: As @Vegamorph suggests, Disting mk4 and Pam's are worth considering, and no difficulty using them. No need for degrees from Harvard University, University of Oxford plus École Polytechnique.
'On ne devrait jamais quitter Montauban' (Fernand Naudin).