Welcome to the forum
To improve the security of your backups, certainly using quality discs is the first thing.
Another thing that can help is to save multiple copies ov very important files in different places.
Avoiding multisession (as you already said) is another thing that can help improving quality.
Writing strategies are embedded in the drive firmware, and that's rather difficult to change them manually. But usually manufacturers knows what they do, so writing strategies decided are usually very reliable (mostly if you use the most recent firmwares).
Another thing that can improve reliability is creating an archive of parity data from each disc you burn with a software like DVDisaster (it's free and opensource, so you can trust in this software too). Saving these parity data in a safe place like an external HDD can help you to recover data from a disc that for some reason became unreadable in some sectors.