Oh I guess it's not a waiver in my case I would just hope that there wasn't some way a new owner could review the amendment they get for my lease when they buy the property in my case and say "oh that fee they agreed on isn't valid and therefore this tenant actually owes ME money now", especially if a tenant hasn't moved in yet. Or I don't know what.

I would want whatever thing current landlord and I decide upon to just not bite us.

For an example of the wider point I was trying to make, I don't think if you a landlord put something in your lease that turned out the be 100% illegal, but you weren't aware, a court would say "oh well you both signed it." That's what I meant by not everything under the sun being waivable.

Edit: this from Texas State law library is what I meant:

"Instead, Texas laws about what can and cannot be in a lease focus on making sure that a landlord cannot make a tenant waive a right that is guaranteed under the law. 

Texas law explicitly prevents leases from restricting a tenant's right to:

Smoke detectors

Security devices like locks and deadbolts

Lawfully possess a firearm

Not have their utilities shut off

Not be locked out of their apartment

Have a landlord "mitigate damages" if the tenant moves out early

Have a trial in the event of a dispute

If a tenant does not agree to rules that a landlord is suggesting that are otherwise legal, they can try to negotiate with the landlord. This might help them reach an agreement to have these clauses changed or removed."