Prop Firm Tech Stack: Broker/PSP choice affecting execution and payouts?

Curious to hear if anyone's had direct experience where the underlying broker/PSP (Payment Service Provider) used by a prop firm noticeably impacted their trading. I'm talking about things like spread widening during news, slippage on larger orders, or even withdrawal processing times. Some firms seem to use very similar backend providers, others claim proprietary tech. For those scaling up accounts, does the prop firm's infrastructure choice eventually become a bottleneck for consistent execution or reliable payouts? Had a situation last month where a significant withdrawal took ages to clear, firm blamed the PSP, made me wonder about the actual relationship and their leverage.