Deadlifts...bent knees or straight knees and why?

Strong thread resurrection

For proper DL form go here to see how they should be done.
https://www.t-nation.com/training/perfecting-the-romanian-deadlift
Straigh leg DL primarily work yor hamstrings and lower back. Back squats done correctly will work your glutes.
Front squats will also work your glutes too but I find them harder to do and also uncomfortable