MIne are now 7 yrs old (yes, for a few days, I have 2 7 yr olds
Remembering back, I gave them a bit of both. I just used up the tin I had at 12 months and then went to plain milk generally. But I did have Toddler formula and I think I used to give taht before bed and / or depending on how the child was eating that day. If they didn't eat much food, they got a formula bottle, if they did, I didn't worry.
I didn't go through much toddler formula at all as I recall, one tin lasted many months.
I was pretty flexible about it all, no strict rule here.
NO allergies or other issues for me to consider though either. In all honesty? I used plain S26 for first bub and Nan for the 2nd because it was a bit cheaper.