How much customization is possible in prop firm software?

It really depends on the software and what the prop firm wants to offer.
The challenge rules can be set based on the firm’s model, including profit targets, daily loss limits, maximum drawdown, minimum trading days, and different account types. The trader dashboard, payment options, risk rules, and trading platform connections can also be adjusted.
This is the approach followed by Hashcodex in its prop firm solutions, where businesses can choose the features and setup that fit their model instead of being limited to a fixed platform.
So, before choosing software, it is worth checking which parts can be changed and which ones are fixed.