The products you linked were all for A6 size/Pocket notebooks. You might consider something larger if you will be writing a lot? It all comes down to what you prefer, what you want to carry around.
I'm a huge fan of the Midori Traveler's notebooks. The regular size is the right amount of room for how much I want to write, and you can use a couple of different inserts to cover different tasks. The Passport size is really nice, if you want something smaller. Amazon has great prices for Traveler's notebooks and inserts, if you want to try them out. Their paper is great, and very fountain pen friendly.
The Story Supply Co cover is super nice, but their paper is not great with fountain pens. I switched out the notebook I got with mine for some Calepino notebooks.
Maruman Mnemosyne is very fountain-pen-friendly and their notebooks are really nice. They make nice pad holders in
A5 or
A4. I've been looking at one of these for my work. So classy!
The Pilot Metropolitan is a great pen, and I love that black one with the dots. I prefer the Pilot medium to the fine, but if you are writing on crappy office paper a lot, a fine nib will work way better. You can swap the nib out of another metro or a kakuno (for that smiley face nib!).