More information would be helpful. For instance what recipes have you already tried? Second what exactly do you want it to be like? Taste like a box cake and be fluffy and moist like a box cake? So why have you been disatisfied with the flavor of the cakes you have made? Given you are looking for a white or yellow I would suggest the flavor is "off" for two reasons. One .as off-putting as you find Leah's post she gave the reason why--their taste is impact by the stabilizers and other chemical agents that are added to them. So if you are looking to replicate something with that taste profile you will have a difficult time doing so. Two the artificial flavors of box cakes will impact their flavor profile. If you are used to those artificial flavor profiles and like them---you will not be able to produce them using quality extracts--the cakes will not have the flavor you are looking for.
As for texture again it will be hard--not impossible--to replicate as it is produced by the chemical agents added to the box mix. Cooks Illustrated has a yellow cake recipe that is designed to replicate the texture of box yellow cakes. The recipe is the Fluffy Layer Yellow Cake--I have tried it. I find it okay, but that is because I do not prefer the ultra-light texture of box cakes--you may find that you like it. Most scratch recipes will not have that texture precisely because that texture is produced by including additives and it is difficult to produce without them.
So what gives? You are looking to produce something from scratch that is made with the inclusion of additives and artificial flavors. If you know this, then you know it is going to be impossible--yes even Cooks recipes only approximates a box yellow cake--to produce what you are looking for--if what you are looking for is the flavor, texture and moistness of box. There are plenty of tried and tested yellow cakes that are moist--but they will not have the texture you are looking for. Most taste great as for yellow cakes, the dominant flavor is yellow--and imo, nothing beats a yellow cake made with homemade vanilla. But if you are looking for a flavor profile that includes chemicals and artificial flavors--no yellow cake will do.
If that is the flavor and texture you want--then by all means use it. As to feeling like cheating (which seems to be the reason you are looking for a scratch recipe) that is a subject that has been beaten to death on this forum. On my view--if it works for you, then use them--be honest with a client if they ask--and most definitely do not beat yourself up about using them. Plenty of people do.
Thank you! It actually helps to know it's probably impossible because much of boxed cake flavor/texture is due to additives. I REALLY think the issue is that I'm used to the flavor of a box cake, it's what I grew up on. I'm sure the cakes I'm trying are coming out how they are supposed to, and I'm just disappointed because it's different that my expectations. I have tried Martha Stewart's Yellow Butter Cake and found it tasted bland (in my opinion), and the outer layer of the cake seemed to crust more than I liked. I tried a Devils Food cake recipe once (Cake Bible maybe, or could have been Martha Stewart) that came out SO moist it was impossible to handle the cakes without them falling to pieces. I started over completely thinking I'd under cooked it. It came out the same the second time. Both of my white cakes involving meringue come out very dry even though I never over beat the eggs. I purposely under cooked a small batch of white cake cupcakes yesterday to see if that would help the dryness (knife came out clean, but just barely),,,,and they were moist right out of the oven, and dry an hour later. I guess I'm just frustrated that four years after trying recipe after recipe I still haven't found "the one". I also want to continue making cakes for people and understand the importance of NOT using a box. So I'm eager to find something that comes out nice, each time. The closest I've come and the recipes that are currently my go-to's are Martha Stewarts Yellow Butter cake, and one called Heavenly White Cake that I found on AllRecipes.com. The white cake is the one I worry about because it is often dry, no matter how I adjust the recipe ( beat eggs less, add more milk). Thanks for the constructive input. I'm just looking for friendly help and advice!