I do a quick set of rdl and then back squat with just the barbell to get myself into a good state of mobility

I used to do stretches between sets of back squat but I cut that out as well l. This likely did me more harm then good. As others have stated, proper bracing / engagement of your core will see you through.

I still pre exhaust on leg extension before back squat but other than that, I feel prepared getting into a good 5*5.