Generally when people refer to soft sex it involves the range between just touching and penetration. This includes oral on or from someone not your partner but not always. The thing is to be 100% clear with each other and the other couple/person/group where the line is drawn. BTW the more people involved the more lines try to get crossed especially if not everyone has the same line. Honestly that is the key to having fun in all aspects of the lifestyle. What you choose to participate in has nothing to do with lingo although it is important to have a basic understanding of something when it is said. The exact definition however is not as cut and dry with lingo as it is with "normal" language because it came into being through use within a small segment of society that needed to have a term for the activity. Most language words terms and phrases have been around for hundreds of years used by everyone versus a small segment thus through use are well defined. Maybe one day "soft swinging" will be as well defined as "raking leaves" but for now it will have to be the definition you choose it to be for you.
Lingo
Soft "swapping" is definitely in the eye of the beholder. Just be sure that you all communicate really well as to what your boundaries are to another couple and be sure you know theirs. It isn't too unusual for people to assume that a phrase akin to "if the chemistry is right we could..." automatically applies to them. Body parts have a tendency to wander when line haven't been clearly drawn. Parties and clubs can have a little more pressure and at times people just forget to communicate well in the heat of the moment. Before you make it that far, though, be sure that both of you are on the same page and support one another. Welcome and good luck.
We are very green when it comes to a lot of this. I understand that swapping would not be considered "soft". But, where is the line? What constitutes being into soft swinging?
Thanks