There is a common tendency to look for gear to make better photographs.
Those of us on forums are, I think, even more susceptible than most. And, dare I say it, men are more susceptible than women.
Don't get me wrong. I love gear at least as much as the next fellow. Ask my wife. .
Reading your post, I would guess that the next light modifier you attach to your strobe is unlikely to do the trick until you are clear in practice about what it is going to do for you. It sounds like you already have some solid, expensive gear.
I recommend adding some inexpensive gear which will help you understand the light better. Fancy gear makes it easier to get good results quickly after you understand how to get good results, but often slows down progress in learning how to get good results. Working more simply forces you to pay attention to what the light is doing instead of focusing on the gear. This helps you use the gear better.
The first thing I would do is make a v-flat. I have plenty of fancy stuff, but the v-flat gets used all the time. You can find instructions on how to make one with google. It is basically a giant reflector which can stand up by itself. It is traditionally two 4x8 foot panels (the size is based on building materials) which connected together along one of the long sides by a "hinge" made of gaffer tape. It could be 3' wide by 6' panels. Some people cut them to 4x7.5' to fit lower ceilings.
Why v-flats? They can be used to block or reflect light. They are big enough for a standing person. They stand on their own. They are easy to move around where you need them. It is easy to understand what they are doing. You have two panels so you can wrap light around your subject. They work with strobes. They work with natural light. They work with hot lights. They work with bounced on-camera lights. They are the easiest tool to use. I use them all the time with people, products, etc.
A v-flat and the tools you already have can make fabulous images. And, once you learn to use the V-flat, you will understand how to use your environment, including white walls (or any neutral color--white, gray or black), ceilings, etc.
The biggest problem I see when a person is starting out photographing people is how to balance the main light (key) with fill light (light which makes the shadows less harsh) and get it to look natural. A white surface you bounce light off of will almost always look natural. A second light source frequently does not.
The second item I would get is something big to diffuse light and something to hold it up. A neutral shower curtain works. So does white "parachute" cloth or rip-stop nylon from the fabric store. Let it hang between your subject and your light (such as your 2' octabox) and you will have a big light source. You can vary how close the curtain is to your subject and how close the light is to the curtain to change the relative "size" of the light. This can give you results like the softbox you are considering, as well as a number of other variations.
Put the v-flat to one side of your subject, as close as possible without getting it in the picture. Start with the "corner" about even with your subject and the white panels towards your subject. If the < is the panel and your subject is the *, it will look something like this: <*
Hang the curtain facing towards the white panel, pointing in front of your subject (feathering the light) and on the other side from the panel. If the curtain is this comma: , your setup looks like this: <*,
Now aim your light towards the curtain (NOTE towards the curtain, not the subject. In front of your subject). In this case, your light is the period: . It looks like this: <*,.
Set this up before your subject comes in. Put a chair where they will be. Or even use yourself as the first subject. Once you have the setup, take a picture of yourself or the chair and get the exposure right (very easy with Profoto TTL). Then bring in your subject (patient partners, children, spouses, siblings or friends are good starting points), take a picture, look at the result, experiment, look at the result, repeat.
Knowledge is power.