toga

You think that's a problem‽ 😅

It does, but there's still some ink in the little section between the feed & stopper, plus ink in the feed itself.

On top of what others have said, it's worth checking that the nib & feed are properly seated. I've had that happen with TWISBI's before and that was the issue.

Quality of knock-off brands like Jinhao and Wing Sung is going to be pretty universally shit. You can usually buy a handful and one will be at least decent though.

That's just not true. I have 35 Jinhao's, and ~25 from other Chinese brands like Moonman/Majohn, Wing Sung, Hongdian, Lemon, Asvine, Kaigelu, & more. Out of all of them, only 2 have been duds; one was a Kaigelu which had a bad nib that I was later able to fix, and the other from a no-name gamble which was horribly unbalanced because they added brass to the finials to make it feel more substantial. The nib was pretty decent though, and it at least looked pretty. Everything else has been fine to excellent. Are they all going to be 5 stars? Of course not, but considering the majority of them were under £20, and around 75% of those were under £10, they've been great. Definitely no worse than Lamy, Kaweco, or any other western brand in that price point. The more expensive ones have all been fantastic.

Granted, there are still some that aren't good and should be largely avoided. Generally, pens that you can't find a brand name for will always be a gamble, as are the 4-digit model number Wing Sung's. They're a different company than the 3-digit ones and I've only ever heard bad experiences about them. But on the whole, Chinese pens have come a long way. Don't be so quick to dismiss them completely.

I'd say #1 or #3, I'm leaning more towards #3

They're well worth trying! I actually prefer the A2, which is kind of their version of the old faceted Decimo. It's made of plastic instead of metal, and as such it's lighter and slightly thinner.

Yes, they are. You can only get these in an EF nib, but it's a good writer.

Jinhao are great for new & experienced users alike. I'd highly recommend the 82, 100, & X159 models. Platinum Preppy's are also excellent budget pens that write far better than a lot of pens in the sub £100 range. The Plasir and Prefounte are basically the same pen but with fancier aesthetics if the Preppy doesn't do it for you. Other pens worth looking at are the Pilot Kakuno & Metropolitan, Kaweco Sport & Perkeo, Faber-Castell Grip, and the Lamy Safari.

Are there any guidelines for the dimensions of the banner?

These are the oranges I've had experience with:

Diamine Blaze Orange (my first & probably favourite) is likely too strong, it leans towards orangered, and Pennonia Róka Koma is almost identical to it. Diamine Pumpkin Shimmer is maybe a touch paler with a gold shimmer. Diamine Deep Dark Orange is a more subdued dark orange & is a fantastic ink. Diamine Peach Punch (Inkvent '21) is an orangey-peach. Diamine Wonderland (Inkvent '21) is a bright yellow-orange. And lastly, Diamine Flame (Inkvent '22) is a good mid orange, and it smells of matches! I haven't had any signs of nib crud from these inks, but YMMV.

As @UnfortunateTwist@beehaw.org mentioned, the Mountain of Ink blog is the best place to go to get a good idea of how different inks look and perform.

I like the 601 so much I bought 2 of them, but with the Sheaffer Triumph-style nib instead of the hooded 51-style nib. The first was a teal plastic body that I absolutely love. It's so well made that it's extremely hard to see where the join between the body and the blind cap are, they blend together perfectly. Then I came across the Flighter version (601a) with the gold trim. It's now one of my most used pens.

Diamine Kong Girls, an ink exclusive to Kong Girls in Hong Kong. It's a lovely purple with an electric blue shimmer, and it never fails to make me happy.