There is a leak where the house meets the trim. After scraping should I use
Regular calking or is there something better to waterproof this area

Is that a painted concrete foundation, or a short wall, and does it stop right where the siding stops? Is there wood behind that row of siding?
(I know you said 'where house meets trim' but I can't envision the whole house.)

Joy that puffiness is where rain water blows into the tool room. It is stucco up
The wood trim. They have used caulking in the past. I was wondering if maybe there is something better to use, maybe more waterproof protection.

I think you need another row of trim at the bottom, slid up behind and gently attached.
Better might be 3" of aluminum flashing. You could work it behind there with a lot of caulk.
Otherwise it won't matter if you use good silicone 40 year caulk, or epoxy paint.
The trim should not have stopped where it did. Water always works its way behind the bottom row of siding.
Whichever you do, scrape and paint with epoxy, or caulk, it will peel again, because you can't get to the critical area behind the trim.

+2 with what Joy said... good advice.
I like flashing more than caulk alone...if backing paint lifts you have an entry point for water again (as it can wick upward a certain distance), and you don't want to goop up caulk that far because it looks like heck.