Maximum digital level is 0 dB. It doesn't matter which container you use. It may matter which audio encoder you use because chances are there could be some kind of auto-gain setting envolved.
Yes, the absolute maximum level is -0.0dBFS. However, the 'loudness' level is important and calculated differently. For broadcast submission, loudness (usually) must be at -24LUFS integrated (+-2) in the US. The 'recommended' level for on-line content and DVD/BU is -18 to -14LUFS. YouTube and other sites of that type, will lower the level in their re-encode process if it exceeds an arbitrary max level. OTOH, some sites (Spotifiy) will increase the loudness level, if it is low, others (YT) will not. I'm not sure about Vimeo either way.
I made the first compression with the digital standard of - 18 db, the customer must be used to listening to video at 0 db. Coming from broadsast or the norm was + 4 db (betacam).
Prior to using the ATSC and EBU loudness measurement, it was typically a reference level (test tone) at -20dBFS with program audio peaks not exceeding -10dB (-18 / -8 EBU). On-line, DVDs and such, peaks around -3 to -6dBFS. The Betacam's +4dB was a line level voltage measurement (1.2 volts = 0VU).