Is it likely for a mom to make bigger babies as she goes BUT have quicker births?

With multiples usually, the babies will not be "big" because there is only so much room inside a womb. Triplets are usually born weighing 4 pounds and twins weigh around 5.5 at birth. The only birth that is "quick" is C-section. Vagina births are not quick, often they take several hours to complete. The mother will gain experience after each pregnancy which will help her deal with it better but there is nothing she can do to produce a faster vagina birth.

However, as the mother's body adapts after each pregnancy subsequent vagina childbirths may take less time to complete because the vagina will not be as tight as it was previously.

Thanks for the perspectiv. by “multiple” I meant “subsequent”. I’ll edit the OP

Every woman’s different there’s a lot of factors too. Sometimes you see the moms who ate everything in sight their first go around and ballooned but then have smaller pregnancies after. Some women do get a little bigger each time, more than anything they start showing sooner because their stomach muscles have already been stretched, especially if it’s like back to back pregnancies

My manager is about to give birth to her second child and she’s no bigger than her first and that’s probably only because I was putting food in her face on a daily basis

I agree with evey woman being different. All of my wifes vaginal deliveries were less than 8 hours from the water break until the nurse put the pad on her, but we had sex almost every day during her pregnancies and her OB thinks that helped.