In basic rule mechanic terms, moving that fast with a character has no influence on their attacks or shoves.
You could put the Charger feat in, that is however, rather situational.
Everything else is in the wide field of Homebrewing rules.
Yeah, 5th Edition doesn't really do this type of thing. Mutants and Masterminds did, but 5th doesn't really support this. Here's some fun reading for you and your quest for speed. The answer to your question though is "Whatever your DM allows" because this is all in the realm of DM discretion.
So if I run into a monster going 1200 or even 300 feet in 6 seconds as an attack how does that work?.
My goal is that my character runs into monster like the flash. How to make this work?
In basic rule mechanic terms, moving that fast with a character has no influence on their attacks or shoves.
You could put the Charger feat in, that is however, rather situational.
Everything else is in the wide field of Homebrewing rules.
Yeah, 5th Edition doesn't really do this type of thing. Mutants and Masterminds did, but 5th doesn't really support this. Here's some fun reading for you and your quest for speed. The answer to your question though is "Whatever your DM allows" because this is all in the realm of DM discretion.
https://www.dandwiki.com/wiki/Pushing_the_Speed_Limit_(5e_Optimized_Character_Build)#:~:text=Using%20your%20normal%20action%2C%20action,there's%20still%20more%20to%20cover.
You could treat it like fall damage... and apply it to both sides, but you won't like the results...