Paper problem is more complex and I will dedicated another post soon. As for the ballpens, here are the candidates to be used. A clear winner recommended in your comments was Zebra Serasa and I finally have them in my hands. It’s great, feels very confortable and I can produce nice handwriting with it. By other hand I’m afraid the perfect bullpen doesn’t exist (or at least I’ve never seen it). I would like a ballpen that wrote full black, waterproof and stand after being erased. I added Zebra brush disposable pen and Pigma Micron for comparison.
Pilot G-3, my current pen up to know, is full black and can’t be erased. However it’s not 100% waterproof and also its ink tends to spread in the paper. This is related with paper problem. Both Zebra Serasa en Uniball inks are very similar: waterproof but they are not so black and don’t stand after erase. That makes sense since ink Pilot looks more liquid and it penetrates deeper in the paper. Zebra Serasa and Uniball Signo are more “gelatinous”, ink remains in the surface and therefore lines are clearer and it can be erased.
The conclusion is I quite like Zebra Serasa overall and I will give it a chance. Surprisingly Uniball Signo in green and blue colors are perfect in all points so for sure I will use them. Ballpens with “click” and spring are more useful but they could show a gap between nib and case instead of nail behaviour in a pen with a cap. This could produce bad handwriting specially if it’s tiny. It’s not the case with Zebra Serasa since it’s well made with accuracy and that gap is residual.
I hope this is useful for you and together can built a solid knowledge about writing issues.