In V1, you can either have an RP FS that also has an account store configured or you can set up a separate fed server to act as external account partner/IdP. Either can be done and made to work.
Having an account store configured on the RP is usually the easy way to get a way to log into the system with test users. However, the login flow is a little different and you don't end up doing things like mapping incoming claims. So, it depends on what you want to test. If you want an end to end test for your whole scenario, you might not want to build it this way.
It is possible but somewhat painful to have two separate FS's on the same IIS box if you give them separate IP addresses and host names (or possibly if you split by port I recommend against that). The painful part is that the MMC expects only one trust policy file on a given server, so managing both FSs on the same box can be tricky. From the IIS level though, it is totally possible. Not sure how this works with ADFS V2 yet.