Yes, you can use RCI, but the caveat is that there has to be a deposit in order to get an exchange. And then you have to be able to pull that exchange before someone else gets it. There was a time when exchanging was easy and "everybody did it." Lately, the mantra is to "own where you want to vacation," because exchanging is harder than ever, and RCI, especially, tends to tack on multiple fees. That drives up the cost of your vacation. Sometimes it's easier to rent where you want to go, on your terms and timeline. A lot of owners rent their units out, which gives you more options, at the end of the day, than banking on an exchange to come through.
Put another way: I owned Weeks timeshares for years, and eventually sold them all, to buy only WorldMark. I live in Washington State, in the heart of WorldMark resorts. I like shorter stays, but there are tricks to making the most of your WM ownership. The biggest thing you'll be facing is nearly $2,850 in maintenance fees - every year, and it goes up by ~5% every year. Combine that with the RCI membership costs and exchange fees you'll pay, add travel expenses, and the cost of those vacations is going to be pretty substantial. But that's your business and budget.
I guess my point is to recommend exploring exactly what you'll get, and how to make the most of it. Buying WM resale means you won't get any of those fancy perks like Travelshare or Club Wyndham. Some WM resorts (Australia, South Pacific, and Southeast Asia, for example) won't be available to you. That's going to leave basically the North America locations and Fiji. And while RCI has a lot of resorts in their directory, as I said, it can be difficult to exchange into some of those more exotic locations. You may be better off renting exactly what you want when you want to go there.
Caveat emptor. If this is resale, then time can't be that pressing. Slow down and make certain it's a good decision for you. Nobody on Tug has an angle here to steer you wrong, but there are lifetimes of experience people are willing to share. That's why Tug is the best travel site on the Internet.
Good luck!
Dave