If one were planning to switch from the Roman Rite to an Eastern Rite or vice versa, would RCIA or something similar be required?
You need permission from the two bishops involved.
How’s about if one found it more convenient (say it was closer) to attend an Eastern Rite Mass than a Roman Rite Mass. Would it be ok?
Its o.k. to attend the eastern rites, although unless you found yourself in the back woods of Ukraine or Slovakia, its doubtful if it would ever be more convenient to attend.
Also, there is an Anglican Rite Catholic Church within an easy drive of my home. Is OK to go? Is communion OK?
Anglican Use churches are o.k. to attend, if you want to attend and receive communion at one of the 6 or so such parishes in the United States you are certainly welcome to.