Some exchanges may have a higher level of trustworthiness than others, but there's always some level of risk involved when using any platform.
Personally, I haven't swapped very large amounts on instant exchanges before, as I tend to prefer the added security of using a traditional exchange.
I think it really depends on your personal preference and risk tolerance. Splitting up larger transactions into smaller ones can definitely add an extra layer of security, but it can also be more time-consuming and inconvenient.
So, up to you to weigh the benefits and drawbacks and make the decision that feels right for you.