just remake the video after Christmas break, hard to give tips when they are walking through your sword (and you're walking through theirs on their screen)
when more than 2900 are online, the server begins to lag and everyone's ping raises significantly, causes everyone to have some degree of delay and there are pretty frequent lag spikes

if you wanted to continue sparring with a high ping, I'd just say to spar as defensively and patiently as possible - any bit of delay causes sparring to go from proactive/reactive to predictive, so the best way to win is waiting for your opponent to make mistakes and run into your sword rather than making your own moves

the huge majority of upper-tier sparrers are very aggressive and offensive, and you just can't spar that way when the server is the way it is right now - for example, comboing a player is extremely difficult because the added delay time makes it impossible to react to where your opponent moves and you basically have to go from relying on a sharp reaction time to getting lucky and making the correct guess