I see both of these spiders (and others) frequently on hiking trips outside of Taipei. Their large webs are often high overhead between trees but can be right across a hiking trail that hasn't been used in a few days, which can make for some excitement.
The two individuals shown in the photos were quite large; both had a body length of about 5 cm not counting legs.
They have similar body shapes but very different color. I don't know if they are completely different species, or different sex or different age.
I mostly see "Spider #2", and usually they are around 3-4 cm in body length. I see "Spider #1" much less frequently, and I don't think I have ever spotted a smaller individual, but that could just be due to lower frequency.
I spotted this on on this plant, but once disturbed he started climbing up a vertical thread back into the threes.
I see these more often than Spider #1.
Adjusted brightness, contrast, sharpness to make the structure of the web more visible:
Spare photos: 1