We have been members for 34 years and most of the time you pick your own site. South Jetty in Oregon used to assign you a site but not any more. Full hookup sites are hard to come by. Usually you have to get on a list then check in each morning to see if there is a full hookup site for you. I have never been turned away because I could not find a site big enough for my 40 ft 5th w. I have downsized now. TT is not nearly as good as it used to be but still better than most. IMHO the parks in Oregon and Wash are the best in the system { that is where we spend our summers}
Sometime TT lets Caravans use the park, usually a small section only. I have never been told that we could not use a TT Park in our 34 years as members and we spend about 150 days/nights in the TT Parks