A couple of other things to bear in mind as you experiment...
MODERN/TRADITIONAL PAIRINGS - There is a great thread in this group on 2 knife pairings. By far, the most common is what you describe -- a large modern folder backed up by a small traditional. My preference is for the reverse -- a large traditional single blade folder backed up by a small, modern mutlitool. Either way, you're drifting into the realm of multiple knife carry. Don't worry. This is a judgement free zone. Lots of us carry more than one.
CARRY METHOD - With modern knives, there is one standard way to carry and that is clipped to your front pocket. With traditionals, you need to think and experiment with other methods. The most common (I think) is to simply drop a small traditional pocket knife in your RFP where God intended them to be carried. But, if you already have a modern knife gnawing away at the fabric of your RFP, you may have trouble getting the traditional out. Another option is to move the small traditional to your LFP or if it's small enough, to your coin pocket if your pants has one. And yet another option is to move your large folder to a rear pocket. Some guys use rear pocket sheaths. I just sew a vertical seam up my jeans pockets for easy rear pocket carry. Lastly, you can move your large folder to your belt in a holster. Yes, there are still guys who carry folders in holsters. I raise the options of carry to point out that WHERE you carry is related to WHAT your carry. If you carry loose in a front pocket, you will likely find that thinner and lighter is generally better. If you carry in your coin pocket, there is a length limit. If you can cope with holster carry, your options increase to allow you to carry a brass brick if you want.
BLADE & TOOL USE - If your already carrying a large modern folder, you might thing more about what you want from a secondary carry in terms of use. You might not know yet and that's what the experimentation is for. If you are creeped out by germs or if you regularly dunk your work knife in hazardous materials, you might want a traditional that you can use for food, like cutting a sub sandwhich or cutting an apple. If you want to whittle, you likely want at least one shorter pen or sheepsfoot/wharncliff type blade. Do you want a cap lifter? The beer scouts might be worth looking at. Do you want scissors? The small SAKs or the Case Peanut with scissors might be a good option. The old Camillus Cub Scout will give you an awl and a cap lifter in a small package.
Hope this helps.