Onboarding speed and slippage for larger accounts

Curious to hear from others managing larger accounts with prop firms—how are you finding the onboarding KYC process? Specifically, is there a noticeable difference in the speed and friction when you're looking to fund a substantial sum? Also, once through, has anyone experienced significant slippage or widened spreads during high-impact news events with the brokers their prop firm uses, especially on instruments like $EURUSD or $GBPUSD when you're moving meaningful size?