Technically, it could be done ... IF. I have done work by remote, but it generally does not include grading because it's harder (more expensive) to get accurate existing grade information. Then, when it comes to a retaining wall, if you are required to have an LA or engineer design it, that person will probably need to be registered to perform design work in your state. Getting casual advice -- like you might get from this forum -- might be more useful for a DIY project, or as an aid to thinking things through. But as planning which you can build from? That is more involved.

If we're doing a remote design like that, generally we'll only do it if it's a local contractor providing us with all the measurements, grades, and photos, and they're willing to run back out as needed for additional data. We do a detailed conceptual drawing, and then the local contractor hands the CAD file off to a local structural engineer for calculations and stamp. That way they're getting something way more attractive and functional than an engineer would design (no offense, engineers, but...) but the part that could kill someone is addressed locally. Plus it reduces the cost as the engineer's only getting paid for engineering.

That said, the best designs are going to come from someone with boots on the ground. If that's an option, that's usually your best option.