I know it's 90cm max. height, but what would the course mainly consist of, I know it may vary from venue to venue. Would some of the fences be similar to novice level hunter trials?
No, would be bigger than a novice hunter trials, but very straight forward. No really complex combinations, inviting water and only occasionally an open ditch.
Probably a bit more visually imposing than a hunter trial too. The jumps will be straightforward but they will be consistently up to height and should be dressed properly.
You will often get a bank or some steps. Usually some water to paddle though (sometimes with a small jump on the way out). A couple of combinations but nothing too technical.
If there is a corner, there is usually an alternative.
When I first did Intro, the main difference xc I found was how solid the jumps were, much more imposing. Nothing too difficult though and it's great to go round a well built course.
Id say an intro is probably an intermediate unaffiliated level. Like others have said, it'll probably look a bit scarier simply because its all better built and they put more effort into making fences look pretty with flower pots etc.! Courses differ as to how challenging it is. Some Id say are really straight forward, others Id say probably arent first time ones.