I’ve used a couple of my period undies for incontinence issues. They seem to hold up pretty well depending on how much I’ve leaked 🙁 Of course if there is a large collection or a collection over the day, it might start to have compression leaks if/when you sit down.
I have one period undies that came with an insert with the option to buy more. The undies itself are absorbent and has a water-proof liner. It can be used on its own or with an insert. Adding the insert allows you to swap it out (if you purchased more) or use the undies as your backup.
I don’t see why you couldn’t use a period panty and double it up with a cloth pad liner for the extra protection if you wished.
Some period panty companies also offer undies that are specific to incontinence. I’m not positive what the difference is or if they add different or extra absorbent layers.
One suggestion that I’d make is to look for the undies that have protection from front to back all the way to the waistline. I was leaning back one day and had a coughing fit that caused my leaking to climb up and over low coverage undies 🙁