The work is your portfolio, not the format of the portfolio.
In my experience, people looking to hire designers will not pay attention to overly complicated portfolios, where you have to click around alot to browse the work. They don't want it interactive, if that means 50% more clicks for them.
The simpler the navigation, the easier you make it for these people to view your work. I have hired people myself and never truly looked at their website specifically, but instead focused on the work they've made for their own clients.
So, to advise on the above, go with the first choice of each:
- A4 landscape PDF, one piece per page with short description.
- Adobe portfolio, which is great, because it can also be used to forward to your own custom domain without making another website. A custom website (Wordpress or whatever) will take up much more time (and possibly, money) for you to build in a bug free manner.
- I don't think you need an interactive PDF, but if you really do, make it simple. You don't need a big red button to go to the next page in a PDF.
Whatever you do, make sure it is bug free. If it stops working for some reason, they will likely close the page and move on to the next candidate.